C3.1 Periodic Table Revision Higher
Q1.
The periodic table on the Data Sheet may help you to answer this question.
(a)
Newlands and Mendeleev both designed periodic tables in which the elements were put in
the order of their relative atomic masses.
When the elements are put in this order a few of them are placed incorrectly when
compared with a modern periodic table.
(i)
Give one example of a pair of elements that would be placed incorrectly if they were
in the order of their relative atomic masses.
......................................................... and ..........................................................
(1)
(ii)
Explain why placing these two elements in the order of their relative atomic masses
would not be correct.
...........................................................................................................................
...........................................................................................................................
(1)
(b)
In the modern periodic table the elements are put in order of their atomic (proton)
numbers.
Explain how the positions of the elements in the periodic table are linked to the electronic
structure of their atoms.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 4 marks)
Q2.
The periodic table was developed over about 200 years.
In 1869, a Russian scientist, Dimitri Mendeleev, arranged the 60 known elements into his
periodic table.
Mendeleev put the elements in order of their increasing atomic weights.
Then he put elements with similar chemical properties in the same columns.
He left gaps in his periodic table.
The modern periodic table on the Data Sheet may help you to answer these questions.
(a)
Mendeleev’s periodic table was produced without any knowledge of the atomic structure of
elements.
State why Mendeleev left gaps in his periodic table.
........................................................................................................................
........................................................................................................................
(1)
Page 1
(b)
The modern periodic table was produced with knowledge of the atomic structure of
elements.
The modern periodic table is an arrangement of the elements in terms of their atomic
structures.
Explain how.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)
(Total 4 marks)
Q3.
Read the information about the development of the periodic table and answer the questions
that follow:
The modern periodic table on the Data Sheet may help you to answer these questions.
(a)
Döbereiner suggested that calcium (Ca), strontium (Sr) and barium (Ba) were also a triad.
Use relative atomic masses to explain why.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)
Page 2
(b)
Suggest why Döbereiner’s ideas were replaced by those of Mendeleev.
.....................................................................................................................................
.....................................................................................................................................
(1)
(c)
Lithium, sodium and potassium are in Group 1. All these elements react with water.
Describe what you see when potassium is added to water.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(d)
In terms of electronic structure, explain why:
(i)
elements in the same group of the periodic table have similar chemical properties
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
transition elements have similar properties even though they are not in the same
group
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(iii)
in Group 1, lithium is less reactive than potassium.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(Total 9 marks)
Q4.
Lithium is a very reactive metal.
(a)
Lithium reacts with cold water.
Page 3
(i)
Which physical property of lithium is seen during this reaction?
..........................................................................................................................
(1)
(ii)
Which chemical property of lithium will be shown by the universal indicator?
..........................................................................................................................
(1)
(b)
Complete the sentence by writing in the missing numbers.
Lithium has an atomic number of 3 and a mass number of 7.
This means that an atom of lithium has .................... protons .................... electrons
and ....................... neutrons.
(3)
(Total 5 marks)
Q5.
The following article appeared recently in the Manchester Gazette.
Sodium Drum Blaze Scare
A 20 litre drum containing sodium burst into flames when it
reacted violently with rainwater at a Manchester factory. It is
believed that the sodium, which is normally stored under oil, had
been accidentally left outside with the lid off.
A factory worker put out the blaze before the fire services
arrived, and a leading fire fighter said, “It was fortunate that
potassium wasn’t involved as it would have reacted more
violently and exploded. These Group 1 alkali metals can be very
dangerous”.
(a)
Group 1 metals are stored under oil.
Suggest why.
....................................................................................................................................
(1)
(b)
Balance the equation which represents the reaction between sodium and water.
Na
+
H2O
→
NaOH
+
H2
(1)
(c)
Explain why the Group 1 metals are called the alkali metals.
....................................................................................................................................
....................................................................................................................................
(1)
Page 4
(d)
Explain, in terms of electrons, why potassium reacts more violently than sodium.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(3)
(Total 6 marks)
Q6.
Three elements in Group 2 of the periodic table are beryllium (Be), magnesium (Mg) and
calcium (Ca). Their mass numbers and proton numbers are shown below. The electronic
structure is shown for beryllium and calcium.
(a)
In a similar way, draw the electronic structure for magnesium.
(3)
(b)
•
The three elements have similar chemical properties
•
The reactivity of these elements with non-metals, increases from beryllium to
magnesium to calcium.
Explain these two statements in terms of atomic structure.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(6)
(Total 9 marks)
Page 5
Q7.
(a) What is the name given to the block of elements in the middle of the Periodic Table
which includes vanadium?
.....................................................................................................................................
(1)
(b)
Some of the properties of vanadium are shown in this list.
•
It has a high melting point.
•
It is a solid at room temperature.
•
It is a conductor of electricity.
•
It is a good conductor of heat.
•
It forms coloured compounds.
•
If forms crystalline compounds.
•
It forms compounds that are catalysts.
Select two properties, from the list above, which are not typical of a Group 1 metal.
1 .................................................................................................................................
2 .................................................................................................................................
(2)
(Total 3 marks)
Q8.
Complete the table which shows some of the physical properties of bromine, chlorine and
iodine.
Melting point
in °C
Boiling point
in °C
Physical state
at 23 °C
Colour of
vapour
Bromine
–7
58
………………..
………………..
Chlorine
–101
–34
………………..
greenish
Iodine
–114
183
………………..
………………..
(Total 2 marks)
Page 6
Q9.
A teacher demonstrated the reactivity of the halogens to some students.
Halogen vapour was passed over heated iron wool in a fume cupboard.
The teacher’s observations are shown in the table below.
Observations
During the reaction
After the reaction
Bromine The iron wool glowed
A red–brown solid had been produced
Chlorine The iron wool glowed
A dark brown solid had been produced
Iodine
(a)
The iron wool did not glow
A black solid had been produced
From these observations what conclusion can be made about the order of reactivity of the
three halogens?
Explain your conclusion.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)
(b)
In terms of electronic structures, explain why iodine is less reactive than bromine.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)
(Total 5 marks)
Page 7
Q10.
In sea water the bromine is present as bromide ions (Br–). The equation below shows how
chlorine can be used to displace bromine from sea water.
Cl2(g) + 2Br–(aq) → Br2(g) + 2Cl–(aq)
Explain, as fully as you can, why chlorine can displace bromine from sea water.
To obtain full marks your answer should refer to electronic structure.
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
...............................................................................................................................................
(Total 3 marks)
Page 8
C3.2 Water Chemistry Revision Higher
Q1.
Rainwater falling on limestone rocks can form caves.
(a)
Complete the sentences by choosing the correct words from the box.
acidic
hard
alkaline
reacts
dissolves
soft
tastes
You may use each word once or not at all.
Rainwater is an ....................... solution which ....................... with limestone. The
solution formed in the lake is known as ....................... water. One advantage of
drinking the water from the lake is that it ....................... better than rainwater.
(4)
(b)
Samples of water were tested by shaking with soap solution. The results are shown in the
table.
(i)
Water sample (50 cm3)
Volume of soap solution
to form a lather in cm3
lake
15
boiled lake
3
rain
1
What is seen when only 10 cm3 of soap solution is shaken with 50 cm3 of water from
the lake?
...........................................................................................................................
(1)
(ii)
Why did the rainwater need only 1 cm3 of soap solution to form a lather?
...........................................................................................................................
(1)
Page 9
(iii)
Why did the water from the lake need 15 cm3 of soap solution to form a lather?
...........................................................................................................................
(1)
(iv)
Explain why boiled water from the lake needed only 3 cm3 of soap solution to form a
lather.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(Total 9 marks)
Q2.
Good quality water is needed for a healthy life.
In the United Kingdom, obtaining safe water for drinking is as simple as turning on a tap. The
water is made safe to drink by water companies.
However, in many parts of Africa and Asia, water used for drinking is contaminated and
untreated. It is estimated that 2.2 million people die each year as a result of drinking
contaminated water.
DADA DANESHANANDA, Man with filtered water from the
Mafi-Zongo water project. www.amurt.net/africa/ghana/2005
(a)
Sea water is not used as drinking water.
Suggest why.
....................................................................................................................................
....................................................................................................................................
(1)
(b)
Explain why water for drinking is filtered and then treated with chlorine.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(Total 3 marks)
Page 10
Q3.
Two problems of hard water are scale and scum, as shown in the pictures of a heating
element and a wash basin.
(a)
Explain the difference between scale and scum
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
Explain how hard water can be made soft using an ion-exchange column.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 4 marks)
Q4.
Water is a natural resource. Drinking water in some parts of the UK is soft, but in other parts
drinking water is hard. Calcium ions in water cause water to be hard. There are two types of
hard water, permanent hard water and temporary hard water.
•
Permanent hard water can be caused by calcium sulfate (CaSO4) dissolved in the water
•
Temporary hard water can be caused by calcium hydrogencarbonate (Ca(HCO3)2)
dissolved in the water
(a)
Temporary hard water causes the formation of scale on heating elements.
Page 11
(i)
Explain how scale forms on heating elements.
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(ii)
Suggest why scale on heating elements causes problems.
...............................................................................................................
...............................................................................................................
(1)
(b)
Permanent hard water can be softened.
(i)
Explain how adding sodium carbonate (Na2CO3) softens permanent hard water.
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(ii)
Explain how a water filter containing carbon, silver and ion exchange resin softens
permanent hard water.
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(Total 7 marks)
Q5.
This information has been taken from two bottles of Australian spring water.
Page 12
(a)
The labels show the names of the ions present in Ridgway and Homeland spring waters.
Describe how these ions got into the water.
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
Both Ridgway and Homeland spring waters are hard.
(i)
There are two ions shown on the labels which make these spring waters hard.
Name one of these ions.
...........................................................................................................................
(1)
(ii)
Ridgway spring water is about twice as hard as Homeland spring water.
Use the information on the labels to explain why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(iii)
Describe how you could use soap solution to show that Ridgway spring water is
about twice as hard as Homeland spring water. You should state how the
experiment is made fair.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
Q6.
The label shows the ions present in the bottle of spring water. This water is temporarily hard.
(a)
Name the compound that would be present in the greatest amount if this water were
evaporated to dryness.
.....................................................................................................................................
(2)
(b)
(i)
What is hard water?
...........................................................................................................................
...........................................................................................................................
(2)
(ii)
State one advantage of hard water.
...........................................................................................................................
(1)
Page 13
(c)
Describe an experiment that would show that this water is temporarily hard.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(d)
This hard water may be softened as shown.
What name is given to this process?
.....................................................................................................................................
(1)
Q7.
The chemical compositions of two samples of hard water, A and B, are shown in the table.
pH
Ions present:
Sample A
Sample B
9
8
Concentration in mg/litre
Ca2+
101
135
Mg2+
2
9
Na+
9
6
HCO3–
299
6
CI–
14
8
SO
2–
4
5
136
NO3–
6
0
Page 14
(a)
What does the pH value tell you about these samples?
.....................................................................................................................................
(2)
(b)
Use the information in the table to explain what is meant by hard water.
.....................................................................................................................................
(1)
(c)
What would be the effect of using temporarily hard water in a kettle?
.....................................................................................................................................
.....................................................................................................................................
(2)
(d)
(i)
Explain which sample of water is permanently hard.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(ii)
How could this hardness be removed?
...........................................................................................................................
(1)
(e)
State one advantage of drinking hard water.
.....................................................................................................................................
(1)
Page 15
C3.3 Calculating and explaining energy changes Revision Higher
Q1.
Methanol can be made when methane reacts with oxygen.
(a)
The energy level diagram for this reaction is shown below.
(i)
What is the energy change represented by A?
...............................................................................................................
(1)
(ii)
Use the energy level diagram to explain how it shows that this reaction is exothermic.
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(b)
A student did an experiment to find the energy released when methanol burns in air.
The student:
•
•
•
weighed a spirit burner containing methanol
set up the equipment as shown in the diagram
recorded the initial temperature
Page 16
•
•
•
•
lit the spirit burner
put out the flame when the temperature of the water had risen by
about 20 °C
stirred the water and recorded the highest temperature of the water
reweighed the spirit burner containing the methanol.
The student repeated the experiment and recorded his results.
Experiment 1
Experiment 2
Experiment 3
Initial mass of spirit burner
and methanol in g
299.3
298.3
296.9
Final mass of spirit burner
and methanol in g
298.3
297.1
295.9
Initial temperature
in °C
23
22
23
Highest temperature
in °C
45
50
43
Temperature change
in °C
22
28
20
Use the diagram and the information in the table to answer the questions.
(i)
The main error in this experiment is energy loss. Suggest one way that the
equipment could be changed to reduce energy loss.
...............................................................................................................
(1)
(ii)
The temperature change in Experiment 2 is greater than the temperature change in
Experiment 1 and Experiment 3. Explain why.
...............................................................................................................
...............................................................................................................
(2)
(iii)
Suggest one reason why the student repeated the experiment.
...............................................................................................................
(1)
(iv)
Use the temperature change in Experiments 1 and 3 to calculate how much energy
is released when 1g of methanol burns. The equation that you need to use is:
Energy released in joules = 100 x 4.2 x mean temperature change
...............................................................................................................
...............................................................................................................
Burning 1g of methanol releases ...................................... J
(2)
(Total 9 marks)
Page 17
Q2.
Read the information about energy changes and then answer the questions.
A student did an experiment to find the energy change when hydrochloric acid
reacts with sodium hydroxide. The equation which represents the reaction is:
HCl + NaOH → NaCl + H2O
The student used the apparatus shown in the diagram.
The student placed 50 cm3 of hydrochloric acid in a glass beaker and measured the
temperature.
The student then quickly added 50 cm3 of sodium hydroxide solution and stirred
the mixture with the thermometer. The highest temperature was recorded.
The student repeated the experiment, and calculated the temperature change each
time.
(a)
The biggest error in this experiment is heat loss.
Suggest how the apparatus could be modified to reduce heat loss.
.....................................................................................................................................
(1)
(b)
Suggest why it is important to stir the chemicals thoroughly.
.....................................................................................................................................
(1)
(c)
Which one of these experiments was probably carried out on a different day to the others?
Explain your answer.
.....................................................................................................................................
(1)
Page 18
(d)
Suggest why experiment 4 should not be used to calculate the average temperature change.
.....................................................................................................................................
(1)
(e)
Calculate the average temperature change from the first three experiments.
.....................................................................................................................................
Answer = .............................. °C
(1)
(f)
Use the following equation to calculate the energy change for this reaction.
energy change in joules = 100 × 4.2 × average temperature change
.....................................................................................................................................
Answer = .............................. J
(1)
(g)
Which one of these energy level diagrams, A or B, represents the energy change for this
reaction?
Explain why.
.....................................................................................................................................
(1)
(Total 7 marks)
Q3.
A student burned four fuels and compared the amounts of energy they produced.
The student set up the apparatus as shown in the diagram.
The heat produced when each fuel was burned was used to raise the temperature of 100 g of
water. The student noted the mass of fuel burned, the increase in temperature and whether the
flame was smoky.
Page 19
The results are shown in the table.
Mass of fuel
burned (g)
Temperature
increase (°C)
Type of
flame
Ethanol
4
24
Not smoky
Methanol
3
9
Not smoky
Peanut oil
2
20
Smoky
Vegetable oil
1
15
Smoky
Fuel
(a)
The student suggested that the vegetable oil was the best fuel for producing heat. Explain
why.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
Suggest an environmental problem that could be caused when large amounts of vegetable
oil are burned. Suggest how the problem could be overcome.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(c)
An energy level diagram for the burning of vegetable oil is shown below.
Which of the energy changes A, B or C:
(i)
represents the activation energy
...............................
(1)
(ii)
shows the amount of energy given out during the reaction?
...............................
(1)
Page 20
HYDROGEN FUEL OF THE FUTURE
Q4.
It has been suggested that hydrogen could be used as a fuel instead of the fossil fuels that are
used at present. The equation below shows how hydrogen burns in air.
2H2 + O2 → 2H2O + heat
The hydrogen would be made from water using energy obtained from renewable sources such
as wind or solar power. The water splitting reaction requires a lot of energy.
(a)
Hydrogen was successfully used as a fuel for a Soviet airliner in 1988.
Why would hydrogen be a good fuel for use in an aeroplane?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
The water splitting reaction is shown in the equation below.
2H2O → 2H2 + O2
Calculate the energy needed to split the water molecules in the equation into H and O
atoms.
2H2O
→
4H
+
2O
.....................................................................................................................................
.....................................................................................................................................
(2)
(c)
On the Periodic Table, hydrogen is placed on its own at the top and in the middle. It is
difficult to position it because it has the properties of metals and non-metals.
(i)
Where would you expect hydrogen to be placed on the periodic table on the basis of
the arrangement of electrons in hydrogen atoms?
...........................................................................................................................
(1)
Explain your answer.
...........................................................................................................................
(1)
(ii)
Give one way in which hydrogen behaves like a metal.
...........................................................................................................................
...........................................................................................................................
(1)
Page 21
(iii)
Give one way in which hydrogen behaves like a non-metal.
...........................................................................................................................
...........................................................................................................................
(1)
(Total 8 marks)
Q5.
Hydrogen could be the fuel used in all cars. One advantage is that when hydrogen reacts
with oxygen only water is produced.
The chemical equation for this reaction is:
2 H2
+
O2
2H2O
This equation can be written showing the structural formulae.
2 H―H
(a)
+
O═O
2H―O―H
Use the bond energies in the table to calculate the energy change for this reaction.
Bond
Bond energy in kJ
H – H
436
O = O
498
O – H
464
........................................................................................................................
........................................................................................................................
........................................................................................................................
Energy change = .............................................. kJ
(3)
(b)
Suggest why the bond energy of O = O is higher than the bond energies of
both H – H and O – H.
........................................................................................................................
........................................................................................................................
(1)
(c)
In terms of bond energies, explain why hydrogen can be used as a fuel
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)
(Total 6 marks)
Page 22
Q6.
Methanol (CH3OH) can be made by reacting methane (CH4) and oxygen (O2) in the
presence of a platinum catalyst. The reaction is exothermic.
An equation that represents the reaction is:
2CH4 + O2 → 2CH3OH
(a)
The energy level diagram for this reaction is given below.
(i)
Use the diagram to explain how you know that this reaction is exothermic.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(1)
(ii)
Explain, in terms of the energy level diagram, how the platinum catalyst increases
the rate of this reaction.
..........................................................................................................................
..........................................................................................................................
(1)
(b)
The equation can also be written showing the structural formulae of the reactants and the
product.
Page 23
(i)
Use the bond energies given in the table to help you to calculate the energy change
for this reaction.
Bond
Bond energy in kJ
C –– H
435
=O
498
C –– O
805
O –– H
464
O
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
Energy change = ...................................... kJ
(3)
(ii)
In terms of the bond energies, explain why this reaction is exothermic.
..........................................................................................................................
..........................................................................................................................
(1)
(Total 6 marks)
Q7.
You will find the information on the Data Sheet helpful when answering this question.
This equation shows the reaction between ethene and oxygen.
C2H4
+
3O2
→
2CO2
+
2H2O
The structural formulae in the equation below show the bonds in each molecule involved.
Page 24
Use the three stages shown at (a), (b) and (c) below to calculate the nett energy transfer when
the formula mass (1 mole) of ethene reacts with oxygen.
(a)
Write down the bonds broken and the bonds formed during the reaction. (Some have
already been done for you.)
(2)
(b)
Calculate the total energy changes involved in breaking and in forming all of these bonds.
(Some have already been done for you.)
(4)
(c)
Describe, as fully as you can, what the figures in (b) tell you about the overall reaction.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
Page 25
C3.4 Further analysis and quantitative chemistry Revision Higher
Q1.
The label is from a packet of Low Sodium Salt.
(a)
A student tested some Low Sodium Salt to show that it contains carbonate ions and
chloride ions.
(i)
Describe and give the result of a test for carbonate ions.
...........................................................................................................................
...........................................................................................................................
(ii)
A student identified chloride ions using acidified silver nitrate solution. State what you
would see when acidified silver nitrate solution is added to a solution of Low Sodium
Salt.
...........................................................................................................................
(1)
(iii)
Flame tests can be used to identify potassium ions and sodium ions. Suggest why it
is difficult to identify both of these ions in Low Sodium Salt using a flame test.
...........................................................................................................................
(1)
(
Q2.
Tennis players sometimes use smelling salts to help revive them. The active chemical in
smelling salts is ammonium carbonate, (NH4)2CO3. Describe how smelling salts can be tested to
show that they contain ammonium ions and carbonate ions. Give the results of the tests.
(a)
Test and result for ammonium ions
....................................................................................................................................
....................................................................................................................................
(2)
(b)
Test and result for carbonate ions
....................................................................................................................................
....................................................................................................................................
(2)
(Total 4 marks)
Page 26
Q4.
(a) Four bottles of chemicals made in the 1880s were found recently in a cupboard during
a Health and Safety inspection at Lovell Laboratories.
The chemicals are correctly named.
You are provided with the following reagents:
•
aluminium powder
•
barium chloride solution acidified with dilute hydrochloric acid
•
dilute hydrochloric acid
•
silver nitrate solution acidified with dilute nitric acid
•
sodium hydroxide solution.
(i)
Describe tests to show that these chemicals are correctly named.
In each case give the reagent(s) you would use and state what you would see.
Test and result for carbonate ions:
...........................................................................................................................
...........................................................................................................................
Test and result for chloride ions:
...........................................................................................................................
...........................................................................................................................
Test and result for nitrate ions:
...........................................................................................................................
...........................................................................................................................
Page 27
Test and result for sulfate ions:
...........................................................................................................................
...........................................................................................................................
(5)
(ii)
Suggest why a flame test would not distinguish between these four chemicals.
...........................................................................................................................
(1)
(b)
Instrumental methods of analysis linked to computers can be used to identify chemicals.
Describe two advantages of using instrumental methods of analysis.
.....................................................................................................................................
.....................................................................................................................................
(2)
Q5.
A student carried out a titration to find the concentration of a solution of hydrochloric acid.
The following paragraph was taken from the student’s notebook. I filled a burette with
hydrochloric acid. 25.0 cm3 of 0.40 mol/dm3 potassium hydroxide was added to a flask. 5 drops
of indicator were added. I added the acid to the flask until the indicator changed colour. The
volume of acid used was 35.0 cm3.
(a)
What piece of apparatus would be used to measure 25.0 cm3 of the potassium hydroxide
solution?
.....................................................................................................................................
(1)
(b)
Name a suitable indicator that could be used.
.....................................................................................................................................
(1)
(c)
Calculate the number of moles of potassium hydroxide used.
.....................................................................................................................................
.....................................................................................................................................
Moles of potassium hydroxide = ............................................ mol
(2)
(d)
Calculate the concentration of the hydrochloric acid. The equation for the reaction is:
KOH + HCl → KCl + H2O
.....................................................................................................................................
.....................................................................................................................................
Concentration of hydrochloric acid = ........................................ mol/dm3
(2)
(Total 6 marks)
Page 28
Q6.
An oven cleaner solution contained sodium hydroxide. A 25.0 cm3 sample of the oven
cleaner solution was placed in a flask. The sample was titrated with hydrochloric acid containing
73 g/dm3 of hydrogen chloride, HCI.
(a)
Describe how this titration is carried out.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(b)
Calculate the concentration of the hydrochloric acid in mol/dm3.
Relative atomic masses: H 1; Cl 35.5
.....................................................................................................................................
Answer = ................................... mol/dm3
(2)
(c)
10.0 cm3 of hydrochloric acid were required to neutralise the 25.0 cm3 of oven cleaner solution.
(i)
Calculate the number of moles of hydrochloric acid reacting.
...........................................................................................................................
Answer = .......................................... mol
(2)
(ii)
Calculate the concentration of sodium hydroxide in the oven cleaner solution in
mol/dm3.
...........................................................................................................................
Answer = ................................... mol/dm3
(2)
Q7.
(a)
This label has been taken from a bottle of vinegar.
Vinegar is used for seasoning foods. It is a solution of ethanoic acid in water. In an
experiment, it was found that the ethanoic acid present in a 15.000 cm3 sample of vinegar
was neutralised by 45.000 cm3 of sodium hydroxide solution, of concentration 0.20 moles
per cubic decimetre (moles per litre).
Page 29
The equation which represents this reaction is
CH3COOH + NaOH → CH3COONa + H2O
Calculate the concentration of the ethanoic acid in this vinegar:
(i)
in moles per cubic decimetre (moles per litre);
...........................................................................................................................
...........................................................................................................................
Concentration =................................... moles per cubic decimetre
(2)
(ii)
in grams per cubic decimetre (grams per litre).
Relative atomic masses: H = 1; C = 12; O = 16.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
Concentration = .................................. grams per cubic decimetre
(2)
(b)
The flow diagram shows some reactions of ethanoic acid.
Page 30
Give the name of:
(i)
gas A,
............................................................................................................................
(1)
(ii)
alkali B,
............................................................................................................................
(1)
(iii)
ester C,
............................................................................................................................
(1)
(iv)
catalyst D,
............................................................................................................................
(1)
(v)
carboxylic acid salt E.
............................................................................................................................
(1)
(Total 9 marks)
Q8.
(a) Vinegar is used for seasoning foods. It is a solution of ethanoic acid in water. In an
experiment, it was found that the ethanoic acid present in a 15.000 cm3 sample of vinegar
was neutralised by 45.000 cm3 of sodium hydroxide solution, of concentration 0.20 moles
per cubic decimetre (moles per litre).
The equation which represents this reaction is
CH3COOH + NaOH → CH3COONa + H2O
Calculate the concentration of the ethanoic acid in this vinegar:
(i)
in moles per cubic decimetre (moles per litre);
...........................................................................................................................
...........................................................................................................................
Concentration =................................... moles per cubic decimetre
(2)
(ii)
in grams per cubic decimetre (grams per litre).
Relative atomic masses: H = 1; C = 12; O = 16.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
Concentration = .................................. grams per cubic decimetre
(2)
Page 31
C3.5 The production of ammonia Revision Higher
Q1.
Early atmospheres on Earth contained ammonia (NH3).
(a)
(i)
Complete the sentence.
Our atmosphere today is made up of about .............................. % nitrogen.
(1)
(ii)
Today we convert nitrogen back to ammonia mainly for the production of fertilisers.
What do plants convert the nitrogen in these fertilisers into?
...........................................................................................................................
(1)
(b)
The conversion of nitrogen to ammonia is shown.
(i)
When making ammonia, what is one source of hydrogen?
...........................................................................................................................
(1)
(ii)
Apart from ammonia, name one other product formed during this conversion.
...........................................................................................................................
(1)
(c)
The main reaction is the formation of ammonia from nitrogen and hydrogen.
(i)
Complete and balance the equation for this reaction.
.......................(g) + .......................(g) → .........NH3(g)
(2)
(ii)
Name the metal catalyst used in this reaction.
...........................................................................................................................
(1)
(iii)
This reaction does not work successfully at room temperature (20 °C) and needs a
much higher temperature of 400 °C. Explain why.
...........................................................................................................................
...........................................................................................................................
(2)
Page 32
(d)
Draw a diagram to show the arrangement of the electrons in a molecule of ammonia. The
electron arrangement of each atom is hydrogen 1 and nitrogen 2.5.
(2)
Q2.
Ammonia is used in the production of fertilisers. The flow diagram shows the main stages in
the manufacture of ammonia. Study the flow diagram and then answer the questions.
(a)
What is the purpose of the iron in the reactor?
........................................................................................................................
(1)
(b)
In the reactor the equation to produce ammonia is:
N2(g)
(i)
+
3H2(g)
2NH3(g)
The equation shows that the reaction is reversible.
Explain how the reaction reaches an equilibrium.
...............................................................................................................
(1)
(ii)
The best yield of ammonia at equilibrium is produced at a low temperature.
Explain why.
...............................................................................................................
...............................................................................................................
(2)
Page 33
(iii)
The best yield of ammonia at equilibrium is produced at a high pressure.
Explain why.
...............................................................................................................
...............................................................................................................
(1)
(Total 5 marks)
Q3.
Ammonia is made from nitrogen and hydrogen in the Haber process.
N2(g) + 3H2 (g)
2NH3 (g) (+ heat)
Flow Chart for the Haber Process
Effect of temperature and pressure on the amount of ammonia at equilibrium
Page 34
(a)
Use the information given above and your knowledge of the Haber process and reversible
reactions to help you to answer this question.
State which conditions of temperature and pressure would give the highest percentage of
ammonia at equilibrium. Explain why.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(b)
The Haber process uses a temperature of 450 °C and a pressure of 200 atmospheres.
Explain why these conditions are chosen.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
Q4.
In the Haber process, nitrogen and hydrogen react to make ammonia.
N2(g) + 3H2(g)
nitrogen + hydrogen
2NH3 (g)
ammonia
% ammonia present at equilibrium
Pressure in
atmospheres
Temperature in ºC
100
200
300
400
500
10
88.2
50.7
14.7
3.9
1.2
25
91.7
63.6
27.4
8.7
2.9
50
94.5
74.0
39.5
15.3
5.6
100
96.7
81.7
52.5
25.2
10.6
200
98.4
89.0
66.7
38.8
18.3
400
99.4
94.6
79.7
55.4
31.9
1000
99.9
98.3
92.6
79.8
57.5
Page 35
The actual conditions used in the Haber process are usually 450 °C and 200 atmospheres.
(a)
What effect does increasing the pressure have on the percentage of ammonia made? Use
the balanced symbol equation to explain why.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
A lower temperature of 100 °C gives high percentages of ammonia at most pressures.
Why is this temperature not used in the Haber process?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)
(c)
Describe and explain the effect of an increase in the temperature on the reaction between
nitrogen and hydrogen in the Haber process.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 6 marks)
Page 36
C3.6 Alcohols, Carboxylic Acids and Esters Revision Higher
Q1.
The structures shown are of the first two members of a homologous series of organic
compounds.
Methanol
(a)
(i)
Ethanol
Complete the diagram for propanol, the next member of the homologous series.
C―C―C
Propanol
(1)
(ii)
Which one of the statements about ethanol is correct?
Tick ( ) one box.
Statement
Tick ( )
Ethanol dissolves in water to form a neutral solution.
Ethanol reacts with sodium to produce chlorine.
Ethanol does not burn in air.
(1)
(b)
Ethanoic acid (CH3COOH) can be produced from ethanol (CH3CH2OH).
(i)
What type of reaction happens when ethanoic acid is produced from ethanol?
...............................................................................................................
(1)
(ii)
State one use of ethanoic acid.
...............................................................................................................
(1)
(Total 4 marks)
Page 37
Q2.
The structures shown are of the first three members of a homologous series of alcohols.
(a)
(i)
Draw a ring around the correct general formula for alcohols.
CnH2n+1OH
C2nH2n+1OH
CnH2n+2OH
(1)
(ii)
What is the formula of the functional group for alcohols?
...............................................................................................................
(1)
(b)
Ethanol is the alcohol used in alcoholic drinks.
(i)
When ethanol dissolves in water the solution formed is not alkaline.
Tick ( ) the reason why the solution formed is not alkaline.
Reason
Tick ( )
Ethanol can be used as a solvent.
Ethanol dissolves in water to form hydroxide ions.
Ethanol has only covalent bonds in its molecule.
(1)
(ii)
Ethanol is used as a fuel because ethanol burns in oxygen.
Complete and balance the chemical equation for this reaction.
C2H5OH
+
................O2
→
2 CO2
+ ................
(2)
(c)
Ethanol can be oxidised to produce the compound shown.
Page 38
(i)
Draw a ring around the correct answer to complete the sentence.
acidic.
When this compound dissolves in water, the solution formed is alkaline.
neutral.
(1)
(ii)
Ethanol reacts with this compound to produce the organic compound shown.
C2H5OH
+
CH3COOH
→
CH3COOC2H5
+
H2O
Complete the sentence.
The type of organic compound produced is ......................................... .
(1)
(Total 7 marks)
Q3.
(a)
This label has been taken from a bottle of vinegar.
Vinegar is used for seasoning foods. It is a solution of ethanoic acid in water.
In an experiment, it was found that the ethanoic acid present in a 15.000 cm3 sample of
vinegar was neutralised by 45.000 cm3 of sodium hydroxide solution, of concentration
0.20 moles per cubic decimetre (moles per litre).
The equation which represents this reaction is
CH3COOH + NaOH → CH3COONa + H2O
Calculate the concentration of the ethanoic acid in this vinegar:
Page 39
(i)
in moles per cubic decimetre (moles per litre);
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
Concentration =................................... moles per cubic decimetre
(2)
(ii)
in grams per cubic decimetre (grams per litre).
Relative atomic masses: H = 1; C = 12; O = 16.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
Concentration = .................................. grams per cubic decimetre
(2)
(b)
The flow diagram shows some reactions of ethanoic acid.
Page 40
Give the name of:
(i)
gas A,
............................................................................................................................
(1)
(ii)
alkali B,
............................................................................................................................
(1)
(iii)
ester C,
............................................................................................................................
(1)
(iv)
catalyst D,
............................................................................................................................
(1)
(v)
carboxylic acid salt E.
............................................................................................................................
(1)
(Total 9 marks)
Page 41
C3.1 Periodic Table Revision Higher Markscheme
M1.
(a)
(i)
argon and potassium or tellurium and iodine or cobalt and nickel
accept correct symbols
allow argon and calcium
1
(ii)
it would place them in incorrect groups (owtte)
idea of not being placed with elements which have similar
properties or converse argument
accept would not have same number of electrons in outer shell
allow it would put them in wrong period if linked to argon and
potassium / calcium
do not accept reasons based just on protons
do not accept metals and non-metals mixed up
1
(b)
any two from:
•
each successive atom has one more electron
•
atoms in the same group have the same number of electrons
in their outer shells / energy levels
number of electrons in outer shell = group number
•
across a period an energy level / shell is being filled
•
in the next period the next energy level / shell is being filled
accept period number = shell number
2
[4]
M2.
(a)
for undiscovered elements
1
(b)
because the elements are in order of number of electrons
or proton number
1
because the number of energy levels / shells is the
number of the period
1
because the number of electrons in the outer energy level /
shell is the number of the group, except in the case of the
noble gases
1
[4]
Page 42
M3.
(a)
40 (Ca) + 137 (Ba) ÷ 2 = 88.5
accept a recognition that the average is near 88
or it is the average of the other two
accept Sr is midway between Ca and Ba
1
(b)
eg newly discovered elements / atoms didn’t fit (into triads) or didn’t
apply to all elements / atoms or lot of exceptions
he = Döbereiner
ignore Mendeleev left spaces or not enough evidence
1
(c)
any two from:
•
fizzes / bubbles / gas
hydrogen alone is insufficient
ignore incorrect name if ‘gas’ stated
•
violent / vigorous / explodes / very fast reaction
accept container explodes
ignore strong reaction
•
floats / on surface
ignore sinks
•
moves (very quickly)
•
melts (into a ball)
•
bursts into flame
accept (bright) light
ignore colour / glow
•
gets smaller / (reacts to) form a solution / dissolves / disappears etc
•
steam / gets hot (owtte)
ignore alkaline solutions or change in colour etc
2
(d)
(i)
same number of electrons in outer shell
accept energy level for shell
accept a correct reference to a specific group
eg (all) have one electron in outershell / (all) lose one electron
(when they react)
1
(ii)
electrons fill an inner / 3rd shell
accept energy level for shell
accept d-level being filled
accept specific reference to 3rd shell
accept descriptions in terms of 3d & 4s etc
1
Page 43
(iii)
it = lithium
accept energy level for shell or converse reasoning for potassium
outer shell electron closer to nucleus
accept fewer shells / smaller atom
1
more (electrostatic) attraction (to nucleus) / electrons
less likely to be lost
accept less shielding / isn’t much shielding
ignore nucleus has more influence but accept nucleus has more
influence over the outer electron(s)
do not accept magnetic / gravitational attraction
1
[9
M4.
(a)
(i)
low density
accept floats (on water)
1
(ii)
forms an alkaline solution with water
accept alkali (metal) or basic
do not accept group 1 metal
1
(b)
3 or three (protons)
1
3 or three (electrons)
1
4 or four (neutrons)
1
[5]
M5.
(a)
acts as barrier between sodium and air / oxygen / water (vapour)
accept because they are reactive
ignore oil will not react
1
(b)
2Na + 2H2O → 2NaOH + H2
allow multiples / fractions
1
(c)
these metals react with water producing an alkaline solution
or
Page 44
produce solution with pH greater than 7 / high pH
owtte
allow produce OH. ions
not these metals are / form alkalis
ignore ‘strong’ pH
1
(d)
it = potassium
outer electron must be mentioned once for all 3 marks
bigger atom
or
outer shell electron further from nucleus
or
more shells
or
converse argument for sodium less reactive provided sodium is
specified
1
less attraction to nucleus
or
more shielding
not less magnetic attraction
1
outer electron more easily lost
ignore potassium reacts more easily
1
[6]
M6.
(a)
each shell completed correctly
[for written 2.8.2 award 1 mark]
for 1 mark each
3
(b)
idea that
•
chemical reactions of metals, involves losing electrons
for 1 mark
Page 45
•
these three elements have the same number
of electrons in the outer shell/highest energy level
gains 1 mark
but
•
these three elements all have two electrons in
the outer shell/highest energy level
gains 2 marks
All form ions with a 2+ charge gains all 3 of these marks
•
reactivity depends on how easily the electrons are lost
for 1 mark
•
the further the electrons are from the nucleus/the higher
the energy level they are in, the more shells the atom has*
then the more easily they are lost
for 1 mark
•
in calcium the electrons are further from the nucleus than
in magnesium than in beryllium
for 1 mark
or as you go down the group ......
(*not just “the more electrons”....)
6
[9]
M7.
(a)
transition / transitional metals / elements / d-block
for one mark
1
(b)
coloured
catalyst
(accept high melting point)
for 1 mark each
2
[3]
M8.
one mark for all the three physical states and one mark for both colours, i.e. marks are for
fully correct columns
liquid red or brown
accept orange
gas
solid
purple
accept violet
[2]
M9.
(a) the conclusion is that chlorine and bromine are more reactive
than iodine
1
any suitable comparisons about the
Page 46extent to which the iron
wool glowed eg because iron glowed with chlorine and bromine
but did not glow with iodine
1
(b)
iodine is less reactive than bromine because the iodine (atom)
is bigger or outer electrons (level / shell) further from the nucleus
accept converse for bromine
1
therefore the forces attracting an incoming electron are
weaker or there is more shielding of the forces attracting
an incoming electron
1
therefore the outer electron gained less easily
Max 2 if no mention of outer energy level / shell or of outer
electron(s)
1
[5]
M10.
chlorine atom smaller than bromine atom / has fewer shells / chlorine is higher in the group
than bromine so it is more reactive
the outer electron / extra electron is more strongly attracted with chlorine than bromine / bromide
(owtte) / more shielding with bromine / less shielding with chlorine
an extra electron is more easily gained by chlorine or chlorine can take an electron from
bromide ion (not bromine)
for 1 mark each
[3]
Page 47
C3.2 Water Chemistry Markscheme
M1.
(a)
acidic
1
reacts
1
hard
1
tastes
1
(b)
(i)
scum / no lather / precipitate
1
(ii)
rain water is soft / pure / nothing dissolved / no limestone
not distilled
1
(iii)
lake water is hard / not soft / contains calcium compounds / dissolved limestone
not impurities
1
(iv)
softened by boiling / loses hardness
1
temporary hardness removed / decomposition of calcium salts
1
[9]
M2.
(a)
contains (large amounts of) dissolved solids / difficult to remove dissolved solids
allow salty / too much salt
allow sea water makes you thirsty / vomit
allow polluted / untreated / contaminated
1
(b)
filtered: removes solids / removes insoluble material / dirt
ignore large objects
1
chlorine: kills/destroy bacteria/microbes/ germs etc
allow disinfect / sterilise or gets rid of bacteria
ignore purify / clean
1
[3]
Page 48
(a) scale – (solid) formed when heat decomposes dissolved calcium / magnesium
compounds owtte
allow: scale is formed when hard water is heated / boiled (to leave
magnesium / calcium compounds)
M3.
scale is calcium carbonate / CaCO3 or magnesium carbonate / MgCO3
ignore evaporate
1
scum – (ppt) formed when soap reacts with calcium / magnesium (ions) owtte
allow scum is formed when hard water reacts with soap
scum is calcium stearate / magnesium stearate
1
(b)
calcium (ions) / Ca2+ / magnesium (ions) / Mg2+
1
replaced by hydrogen ions / H+ / sodium ions / Na+
1
[4]
M4.
(a)
(i)
on heating, the calcium hydrogencarbonate decomposes
1
forming a scale of insoluble calcium carbonate
1
(ii)
the scale reduces the efficiency of the heating element
or the scale increases energy costs / uses more energy
1
(b)
(i)
the sodium carbonate / carbonate ions react with calcium /
magnesium ions, forming a precipitate of calcium
carbonate / magnesium carbonate
1
therefore the water is softened because this removes the
calcium / magnesium ions, which cause hardness, from
the water
1
(ii)
sodium / hydrogen ions are present in the ion exchange resin
1
Page 49
therefore the water is softened because these ions take
the place of calcium / magnesium ions that cause
hardness in the water
1
[7]
M5.
(a)
water came into contact with rocks / ground / soil
ignore mountains
erode gets first mark
1
ions or compounds or chemicals or they dissolved / soluble / leached / reacts /
forms a solution
do not accept gets picked up
accept water dissolves them from the rocks for 2 marks
1
(b)
(i)
calcium or magnesium
accept Ca2+ or Mg2+ or Ca or Mg
do not accept Ca+ alone
1
(ii)
answers must involve both calcium and magnesium
totals required for 2 marks
Ridgway: Ca + Mg = 53
1
Homeland: Ca + Mg = 27
accept there is (almost) twice as much
Magnesium and Calcium in Ridgway water for 1 mark
1
(iii)
equal volumes / quantities / amounts of water
1
add soap with / shaking / mixing / agitation
same amounts of soap = max 2
do not accept just add
do not accept solid soap
1
the harder sample (Ridgway) needs 2 × more soap to give lather
or the less hard sample (Homeland) needs half as much
soap to give lather can get twice as much scum with harder
(Ridgway) sample
1
[8]
Page 50
M6.
(a)
calcium
allow formulae
1
carbonate
1
(b)
(i)
soap
allow 2 marks for
“contains CaSO4 / Ca(HCO3)2 / Ca2+ / Mg2+”
1
forms scum / no bubbles / no lather
allow 1 mark for “contains Ca / Mg”
do not allow “contains CaCO3”
1
(ii)
taste / strengthen bones, teeth etc / health reason e.g. less heart
disease / makes better beer
1
(c)
(shake with) soap; makes scum / no lather
1
boil (a fresh sample)
1
retest with soap
1
result/comparison
alternative answers:
boil (not to dryness)
cloudiness in water/some deposit formed
if a comparison is made with a sample of a soft water, a further 2
marks would be possible
1
(d)
ion-exchange
1
[10]
Page 51
M7.
(a)
weak
not slightly
2
alkaline / base
mark independently
1
(b)
contains Ca2+ / Mg2+ / named calcium
compound / correct formula
do not accept reference to soap not calcium / magnesium
1
(c)
build up of fur / scale / forms CaCO3/ precipitate formed
not ‘scum’
wastes energy / less efficient / takes longer to boil
1
(d)
(i)
sample B
1
contains (calcium) sulphate / SO42–
1
not softened by boiling / does not contain many HCO3– ions / cannot
precipitate CaCO3
1
(ii)
by use of ion-exchange / washing soda / distillation
not detergent / soap
1
(e)
strengthen bones, teeth / taste
not good for you / healthier
1
[10]
Page 52
C3.3 Calculating and explaining energy changes Markscheme
M1.
(a)
(i)
activation energy or energy needed to start the reaction
1
(ii)
the reaction is exothermic because the energy level /
value of products is less than the energy level /
value of reactants
allow the reaction is exothermic because arrow B goes down
or methanol is below methane and oxygen
or arrow C is bigger than arrow A for 1 mark
allow energy level of products is lower unqualified
or the energy level of reactants is higher unqualified for 1 mark
2
(b)
(i)
use a lid / cover over the calorimeter
or any mention of how the calorimeter could be safely
enclosed / insulated
1
(ii)
a greater mass of methanol was burned in Experiment 2
1
therefore the temperature change was greater because
more energy was transferred / released
1
(iii)
any one from:
•
to improve or check repeatability / quality of results
•
to make it easier to spot an anomalous measurement
•
to be able to calculate an average mean value
1
(iv)
8820 (J)
for correct answer
if answer is incorrect allow one mark for 21 used as the mean
temperature change
2
[9]
Page 53
M2.
(a)
eg plastic (beaker) / insulation / lid / cover or any mention of enclosed
any sensible modification to reduce heat loss
ignore prevent draughts
ignore references to gas loss
1
(b)
all the substances react or all (the substances) react
fully / completely or heat evolved quickly or
distribute heat
accept to mix them
‘so they react’ is insufficient for the mark
accept increase chances of (successful) collisions / collision rate
increase
do not accept rate of reaction increase / make reaction faster
1
(c)
experiment 2 and different / higher / initial / starting temperature
accept experiment 2 and the room is hotter / at higher temperature
do not accept temperature change / results higher
1
(d)
temperature change does not fit pattern
accept anomalous / odd or it is the lowest or it is lower than the
others or it is different to the others
‘results are different’ is insufficient
1
(e)
7 / 7.0
1
(f)
(100 × 4.2 × 7) = 2940
ecf from (e)
1
(g)
diagram A and reaction exothermic / heat evolved / Δ H is negative /
temperature rises
accept energy is lost (to the surroundings)
1
[7]
Page 54
M3.
(a) either:
calculations: all correct (ethanol = 6, methanol = 3,
peanut oil = 10, vegetable oil = 15)
ignore repetition of data from table unqualified
or
implication of correct calculation
(vegetable oil) gives largest temperature / heat increase per gram (owtte)
allow ‘produced most heat in proportion to the fuel used’ owtte for 1
mark
2
(b)
any one from:
owtte
•
smoke
ignore references to crops/food
•
soot
•
carbon
•
carbon monoxide
•
carbon dioxide
•
global warming / climate change / greenhouse gases
•
(air) pollution
•
harmful/poisonous
1
scrub / wash the gases owtte
filter / remove (gases / fumes / appropriate named substance)
owtte
(add extra oxygen) can burn more efficiently owtte
use a cleaner fuel owtte
plant more trees or similar linked to CO2
any sensible answer
‘don’t burn so much fuel’ insufficient alone
ignore extractor fans / air conditioning
1
(c)
(i)
A
1
(ii)
B
1
[6]
Page 55
M4.
(a) low density;
gives out light energy when burnt;
combustion product is not harmful;
any two for 1 mark each
2
(b)
attempt to add bond energies;
e.g. adding O-H bond energies
answer = 4 × 464 = 1856
for 1 mark each
2
(c)
(i)
Group 1:
elements in a group have the same number of electrons in outer shell
first because only one electron
or Group 7:
because needs one electron to complete outer shell
for 1 mark each
2
(ii)
forms H+ ion
for 1 mark
1
(iii)
forms molecules;
low melting point (gases);
or form covalent bonds forms H– ion
for 1 mark
1
[8]
M5.
(a) reactants–
2 × H-H + 1 × O = O
= 1370 (kJ)
1
products–
4 × O-H = 1856 (kJ)
1
energy change = 486(kJ)
1
(b)
O=O has a double (covalent) bond
or
O-H and H-H only have single (covalent) bonds
1
Page 56
(c)
hydrogen can be used as a fuel because when it reacts with
oxygen more energy is released in bond making than used
in bond breaking
1
therefore the reaction releases energy or the reaction is
exothermic
1
[6]
M6.
(a)
(i)
energy / heat of products less than energy of reactants
owtte
allow products are lower than reactants
allow more energy / heat given out than taken in
allow methanol is lower
allow converse
allow energy / heat is given out / lost allow ΔH is negative
1
(ii)
lowers / less activation energy
owtte
allow lowers energy needed for reaction
or it lowers the peak/ maximum
do not allow just ‘lowers the energy’
1
(b)
(i)
bonds broken: (2 × 435) + 498 = 1368
allow: (8 × 435) + 498 = 3978
1
bonds made: (2 × 805) + (2 × 464) = 2538
allow: (6 × 435) + (2 × 805) + (2 × 464) = 5148
1
energy change: 1368 – 2538 = (–)1170
allow: 3978 – 5148 = (–)1170
ignore sign
allow ecf
correct answer (1170) = 3 marks
1
(ii)
energy released forming new bonds is greater than energy needed to
break existing bonds owtte
allow converse
do not accept energy needed to form new bonds greater than
energy needed to break
existing bonds
1Page
57
[6]
Q7
(a)
Bonds broken
number
type
3
[O=O]
each for 1 mark
Bonds formed
type
[O–H]
number
4
2
(b)
Total energy change Total energy change
in breaking bonds in forming bonds
3 × 498 = 1494
4 × 464 = 1856
each for 1 mark
Total = 3758
Total = 5076
each for 1 mark
4
(c)
net energy transfer = 1318
this energy is released in the reaction/it is an exothermic reaction
each for 1 mark
[N.B. credit e.c.f. (a) → (b) and (b) → (c)]
2
[8]
Page 58
C3.4 Further analysis and quantitative chemistry Revision Higher Markscheme
M1.
(a)
(i)
hydrochloric acid / HCl
accept any (named) acid
1
carbon dioxide / CO2
accept bubbles / fizz / gas or limewater gets milky
ignore ‘add limewater’
do not accept other named gases
2nd mark dependant on first mark
accept for this answer only heat gives CO2 / limewater milky = 1
mark
1
(ii)
(white) precipitate / solid
ignore names of substances even if incorrect
accept white deposit / substance
do not accept any coloured precipitate
1
(iii)
eg flame colour of (Na) and flame colour of (K)
interfere / mask / mix with each other
accept ‘can’t see the colours’ or ‘difficult to determine the colour’ or
‘both produce different colours’ or a correct statement of colours or
hard to distinguish
1
(b)
(i)
eg essential (mineral) or everyone
needs it / some (salt) or problems
with health if have no salt
accept preservative / flavouring / taste
it = salt
(all) foods contain / use it / sodium chloride / salt
1
(ii)
mark positively ie no list principle
advantages
any two from:
ignore economic arguments throughout or people eat less salt
•
more people will be healthier
•
(should have) less heart disease
•
(should have) less cancer
Page 59
•
(more people with) lower blood pressure
2
disadvantages
any one from:
ignore references to too much / too little (salt)
•
not everyone affected
•
not enough evidence
•
does not provide choice
•
undemocratic
•
less taste / flavour
ignore no flavour / taste
•
shorter shelf life / not preserved (as long)
ignore references to sell by dates
•
too much potassium chloride might be bad
1
[8]
M2.
(a)
test: add NaOH
allow any group 1 / 2 hydroxide or hydroxide (ions) or OH–
incorrect or no reagent = 0, except add NaOH and aluminium or
heat / warm could get result mark
1
result: gas turns (red) litmus blue / ammonia is given off
accept alkaline gas / ammonia produced
do not accept blue litmus turns blue
allow any acid-base indicator with correct result
1
(b)
test: add (dilute) acid
named acid
incorrect or no reagent = 0
1
result: gas gives (white) solid / precipitate with limewater
or goes white with limewater
accept CO2 produced
gas turns limewater milky / cloudy / white (ignore misty)
allow calcium hydroxide for limewater
1
[4]
Page 60
M3.
(a)
sodium carbonate / sodium hydrogencarbonate / sodium bicarbonate
Na2CO3 / NaHCO3
ie
sodium / sodium ions (1 mark)
carbonate / carbonate ions
(1 mark)
incorrect formula including Na and
CO3 = 1 mark
2
(b)
calcium chloride
CaCl2
ie calcium / calcium ions (1 mark) chloride / chloride ions (1 mark)
incorrect formula including Ca and Cl = 1 mark
2
(c)
iron or iron(II) ions
Fe2+ ferrous ions
ignore anions
ignore nickel / chromium
do not accept iron(III) or ferric ions5
1
[5]
Q4
(a)
(i)
each correct test and one result = 1 mark
one other result for any test = 1 mark
this mark can only be awarded once
1
Na2CO3: HCl → (odourless) gas (1)
CO2 / carbon dioxide (1)
1
NaCl: AgNO3 → white ppt (1)
silver chloride (1)
1
NaNO3: Al + NaOH → pungent /sharp smell / choking gas (1)
NH3 / ammonia (1)
1
Na2SO4: BaCl2 → white ppt (1)
barium sulphate (1)
1
Page 61
(ii)
all would give a yellow / yellow-orange
(flame) / same coloured (flame) / same results
allow orange (flame)
or
they all contain sodium owtte
1
(b)
any two from:
ignore cost
•
fast / quick or comment about speed
ignore human error
•
small amounts
accept any valid answer
•
sensitive / accurate
accept operators do not need chemical skills
•
ease of automation
•
sample not used up
•
reliable / efficient
•
can be left to run / continuous analysis
ignore results can be saved
2
[8]
M5.
(a)
pipette / burette
1
(b)
named indicator eg methyl orange / phenolphthalein
not universal
accept litmus but not litmus paper
1
(c)
2 for correct answer
1
= 0.01
Page 62
1
(d)
1KOH ≡ 1 HCl
0.01 moles HCl in 35 cm3
1
= 0.29
2 for correct answer
0.3 = (1) (with correct working = (2))
1
[6]
M6.
(a)
hydrochloric acid in burette
1
indicator
1
note volume at end / neutralisation point
titre must be HC1
1
(b)
1 mole HCl = 36.5g /36.5
1
= 2 moles / dm3
2 for correct answer
1
(c)
(i)
allow e.c.f. ie their (b) ×
2 for correct answer
1
= 0.02 moles
1
(ii)
0.02 ×
= 0.8 mol / dm3
Page 63
1
allow e.c.f. ie their (c)(i) ×
1
[9]
M7.
(a)
(i)
e.g. moles NaOH = moles of acid
or formula:
0.2 ×
= 0.009
15M1 = 0.2 × 45
1
rounding to 0.01 loses mark
= 0.009 ×
= 0.6(M)
M1 = 0.6(M)
ecf for arithmetical error
correct answer 2 marks
1
(ii)
36
ecf – (a)(i) × 60
correct answer 2 marks
0.6 × 60 gets 1 mark
relative formula mass of ethanoic acid
= 60 for 1 mark
0.6 × incorrect molar mass gains second mark only
2
(b)
(i)
A = hydrogen / H2
1
B = sodium hydroxide / NaOH or
sodium oxide / Na2O
1
(iii)
C = ethyl ethanoate (acetate) /
CH3COOC2H5 / CH3CO2C2H5
1
(iv)
D = (concentrated) sulphuric acid /
H2SO4
do not accept dilute sulphuric acid
1
Page 64
E = sodium ethanoate (acetate) / CH3COONa / CH3CO2Na
1
[9]
M8.
(a)
(i)
e.g. moles NaOH = moles of acid
or formula:
0.2 ×
= 0.009
15M1 = 0.2 × 45
1
rounding to 0.01 loses mark
= 0.009 ×
= 0.6(M)
M1 = 0.6(M)
ecf for arithmetical error
correct answer 2 marks
1
(ii)
36
ecf – (a)(i) × 60
correct answer 2 marks
0.6 × 60 gets 1 mark
relative formula mass of ethanoic acid
= 60 for 1 mark
0.6 × incorrect molar mass gains second mark only
2
(b)
(i)
A = hydrogen / H2
1
B = sodium hydroxide / NaOH or
sodium oxide / Na2O
1
(iii)
C = ethyl ethanoate (acetate) /
CH3COOC2H5 / CH3CO2C2H5
1
(iv)
D = (concentrated) sulphuric acid /
H2SO4
do not accept dilute sulphuric acid
1
E = sodium ethanoate (acetate) / CH3COONa / CH3CO2Na
1
[9]
Page 65
C3.5 The production of ammonia Revision Higher Markscheme
M1.
(a)
(i)
78-80%
1
(ii)
proteins
accept amino acids
1
(b)
(i)
natural gas
accept methane (CH4)
accept water (H2O)
1
(ii)
carbon dioxide
1
(c)
(i)
N2 + H2
1
correct balancing 1 + 3 → 2
award only if reactants are correct
1
(ii)
iron
accept Fe
1
(iii)
at low temperatures rate of reaction is too slow
accept very few collisions at low temperatures
accept converse
particles need enough (activation) energy to react
accept particles need enough energy for bonds to break
accept converse
1
(d)
all three covalent bonds displayed correctly as electron pairs
1
two lone electrons displayed not necessarily as a pair
1
[11]
Page 66
M2.
(a)
catalyst
accept speeds up reaction
or
lowers activation energy
1
(b)
(i)
an equilibrium is achieved when rate of the forward reaction
is exactly the same as the rate of the backward reaction
1
(ii)
in this equilibrium the forward reaction to form ammonia
is exothermic
1
therefore if the temperature is low the yield from the
exothermic reaction increases
1
(iii)
in this gaseous equilibrium if the pressure is high this
will favour the reaction that produces the least number
of molecules, that is, the forward reaction to form ammonia
1
[5]
M3.
(a)
2 marks for comments related to temperature
low / lower / lowest temperature (or 100 °C from graph)
ignore references to catalyst
1
any one from:
•
(forward) reaction exothermic
or reverse reaction endothermic
•
if the temperature is increased the yield of product will decrease or
reaction right to left
high temperature favours reverse reaction or reverse argument
the lower the temperature the greater the yield = 2 marks
2 marks for comments related to pressure
1
high / higher / highest pressure (or greater than 200 atm. from graph)
1
any one from:
•
four reactant molecules but only two product molecules (owtte)
reverse reaction goes from 2 molecules / moles / volumes to 4
molecules / moles / volumes
•
increase in pressure favours the reaction which produces
the least number of molecules
decrease in pressure favours the back reaction because it
produces the most molecules
1
Page 67
(b)
any three from:
•
at low temperatures the reaction is too slow
•
450 °C gives a reasonable yield at a fast rate /
compromise between yield and rate (*)
•
200 atm. gives a reasonable yield at a reasonable cost / safely /
compromise between yield and cost / safety (*)
(*) or 450°C and 200 atm / these are compromise conditions for 1
mark
•
catalyst works better at higher temperature
•
(very) high pressures could be dangerous (owtte)
safety factor
•
(very) high pressures are expensive (owtte)
•
(yield is not too important because) unreacted gases can be recycled
3
[7]
M4.
(a)
increases % / amount of ammonia
1
favours the forward reaction
1
(b)
reaction(s) would be too slow
1
(c)
any three from:
•
rate increased
•
decreases % / amount of ammonia
•
the forward reaction is exothermic
•
the backward reaction is endothermic
•
backward reaction favoured / forward reaction not favoured
•
yield / amount of nitrogen and hydrogen increased
•
the relative amount (yield) of ammonia decreases as the
equilibrium is changed
•
the relative amount (yield) of nitrogen and hydrogen increases
as the equilibrium is changed
explanations in terms of particles are neutral
3
[6]
Page 68
C3.6 Alcohols, Carboxylic Acids and Esters Revision Higher Markscheme
M1.
(a)
(i)
7 C-H bonds and 1 C-O-H bond
1
(ii)
ethanol dissolves in water to form a neutral solution
1
(b)
(i)
oxidation
1
(ii)
any one from:
•
in vinegar
•
to make esters
1
[4]
M2.
(a)
(i)
CnH2n+1OH
1
(ii)
OH
1
(b)
(i)
ethanol has only covalent bonds in its molecule
1
(ii)
3 (O2)
1
3H2O
1
(c)
(i)
acidic
1
(ii)
an ester
1
[7]
Page 69
M3.
(a)
(i)
e.g. moles NaOH = moles of acid
or formula:
0.2 ×
= 0.009
15M1 = 0.2 × 45
1
rounding to 0.01 loses mark
= 0.009 ×
= 0.6(M)
M1 = 0.6(M)
ecf for arithmetical error
correct answer 2 marks
1
(ii)
36
ecf – (a)(i) × 60
correct answer 2 marks
0.6 × 60 gets 1 mark
relative formula mass of ethanoic acid
= 60 for 1 mark
0.6 × incorrect molar mass gains second mark only
2
(b)
(i)
A = hydrogen / H2
1
B = sodium hydroxide / NaOH or
sodium oxide / Na2O
1
(iii)
C = ethyl ethanoate (acetate) /
CH3COOC2H5 / CH3CO2C2H5
1
(iv)
D = (concentrated) sulphuric acid /
H2SO4
do not accept dilute sulphuric acid
1
E = sodium ethanoate (acetate) / CH3COONa / CH3CO2Na
1
[9]
Page 70
Page 71