Q1.
Cosmetic powders were widely used in ancient Egypt.
Cosmetic powders that may have been used in face paints have been analysed. These powders
contained compounds that are rare in nature. The compounds must have been made by the ancient
Egyptians using chemical reactions.
Page 1 of 53
One of these compounds is called phosgenite.
Analysis of this compound shows that it contains:
76.0% lead (Pb) 13.0% chlorine (Cl)
2.2% carbon (C)
8.8% oxygen (O)
Calculate the empirical formula of this compound.
To gain full marks you must show all your working.
Relative atomic masses: C = 12 ; O = 16 ; Cl = 35.5 ; Pb = 207
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(Total 4 marks)
Q2.
Perfumes contain a mixture of chemicals.
The main ingredients of perfumes are a solvent and a mixture of fragrances.
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(a)
A sample of the solvent used in one perfume contained 0.60 g of carbon, 0.15 g of
hydrogen and 0.40 g of oxygen.
Relative atomic masses: H = l; C = 12; O = 16.
Calculate the empirical (simplest) formula of the solvent.
You must show all of your working to gain full marks for this question.
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(4)
(b)
Solvent molecules evaporate easily.
Explain why substances made of simple molecules evaporate easily.
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(2)
(c)
Most companies claim that their perfumes have been tested on skin. A study was made of
the tests they used. The study found that each company used different tests.
The perfumes were tested in the companies’ own laboratories and not by independent
scientists.
Some companies did not give any information about the tests that they had used.
(i)
Suggest why companies test their perfumes on skin.
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(1)
Page 3 of 53
(ii)
Did the study show that the tests made by the different companies were valid and
reliable?
Explain your answer.
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(2)
(Total 9 marks)
Q3.
Liquefied petroleum gases such as propane and butane are used as heating fuels for
caravans, boats and barbecues.
(a)
Propane and butane have no smell, so for safety reasons a very small amount of
thioethanol – the smelliest substance known – is added, even though it is toxic in large
concentrations.
Suggest one safety reason why thioethanol is added to propane and butane.
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(1)
(b)
Suggest how mass spectrometry could be used to distinguish between propane (C3H8)
and butane (C4H10).
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(1)
Page 4 of 53
(c)
When 0.4 g of a hydrocarbon gas was completely burned in oxygen, 1.1 g of carbon
dioxide and 0.9 g of water were the only products.
Relative formula masses: CO2 = 44; H2O = 18.
Use this information to calculate the number of moles of carbon dioxide and of water produced in
this reaction. Use your answers to calculate the empirical formula of this hydrocarbon.
You must show all your working to gain full marks.
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Empirical formula is ..............................
(4)
(Total 6 marks)
Q4.
Aspirin tablets have important medical uses.
Page 5 of 53
A student carried out an experiment to make aspirin. The method is given below.
1.
2.
3.
4.
5.
6.
7.
8.
(a)
Weigh 2.00 g of salicylic acid.
Add 4 cm3 of ethanoic anhydride (an excess).
Add 5 drops of concentrated sulfuric acid.
Warm the mixture for 15 minutes.
Add ice cold water to remove the excess ethanoic anhydride.
Cool the mixture until a precipitate of aspirin is formed.
Collect the precipitate and wash it with cold water.
The precipitate of aspirin is dried and weighed.
The equation for this reaction is shown below.
C7H6O3
+
salicylic acid
C4H6O3
→
C9H8O4
+
CH3COOH
aspirin
Calculate the maximum mass of aspirin that could be made from 2.00 g of salicylic acid.
The relative formula mass (M r) of salicylic acid, C7H6O3, is 138
The relative formula mass (M r) of aspirin, C9H8O4, is 180
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Maximum mass of aspirin = .............................. g
(2)
(b)
The student made 1.10 g of aspirin from 2.00 g of salicylic acid.
Calculate the percentage yield of aspirin for this experiment.
(If you did not answer part (a), assume that the maximum mass of aspirin that can be
made from 2.00 g of salicylic acid is 2.50 g. This is not the correct answer to part (a).)
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Percentage yield of aspirin = .............................. %
(2)
(c)
Suggest one possible reason why this method does not give the maximum amount of
aspirin.
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(1)
Page 6 of 53
(d)
Concentrated sulfuric acid is a catalyst in this reaction.
Suggest how the use of a catalyst might reduce costs in the industrial production of
aspirin.
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(1)
(Total 6 marks)
Q5.
Aspirin tablets have important medical uses.
(a)
Aspirin is made when salicylic acid reacts with ethanoic anhydride.
The equation for this reaction is:
C7H6O3
salicylic acid
+
C4H6O3
→
C9H8O4
+
CH3COOH
aspirin
Calculate the maximum mass of aspirin that could be made from 100 g of salicylic acid.
Show clearly how you work out your answer.
The relative formula mass (M r) of salicylic acid (C7H6O3) is 138.
The relative formula mass (M r) of aspirin (C9H8O4) is 180.
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Maximum mass of aspirin = .................................... g
(2)
Page 7 of 53
(b)
(i)
In an experiment a chemist calculated that the maximum yield of aspirin is 400 g.
The chemist did the experiment but only made 250 g of aspirin.
Calculate the percentage yield of aspirin for this experiment.
Show clearly how you work out your answer.
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Percentage yield of aspirin = ........................... %
(2)
(ii)
Suggest one possible reason why the chemist did not have a percentage
yield of 100%.
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(1)
(c)
The use of a catalyst might reduce costs in the industrial production of aspirin.
Suggest how.
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(1)
(Total 6 marks)
Q6.
(a)
This label has been taken from a bottle of vinegar.
Page 8 of 53
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 cm 3 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);
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Concentration =................................... moles per cubic decimetre
(2)
(ii)
in grams per cubic decimetre (grams per litre).
Relative atomic masses: H = 1; C = 12; O = 16.
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Concentration = .................................. grams per cubic decimetre
(2)
(b)
The flow diagram shows some reactions of ethanoic acid.
Page 9 of 53
Give the name of:
(i)
gas A,
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(1)
(ii)
alkali B,
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(1)
(iii)
ester C,
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(1)
(iv)
catalyst D,
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(1)
(v)
carboxylic acid salt E.
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(1)
(Total 9 marks)
Q7.
Silicon is an important element used in the electronics industry.
(a)
Silicon can be made by heating a mixture of sand (silicon dioxide) with magnesium
powder.
The equation for this reaction is shown below.
SiO2 (s)+ 2Mg (s) → 2MgO (s) + Si (s)
Calculate the mass of silicon dioxide needed to make 1 g of silicon.
Relative atomic masses: O = 16; Si = 28
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Mass = ........................................................g
(3)
Page 10 of 53
(b)
The resulting mixture of magnesium oxide and silicon is added to a beaker containing
hydrochloric acid. The silicon is then filtered from the solution.
(i)
The magnesium oxide reacts with the hydrochloric acid and forms magnesium
chloride (MgCl2) solution and water.
magnesium oxide + hydrochloric acid → magnesium chloride solution + water
Write a balanced symbol equation for this reaction, including state symbols.
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(2)
(ii)
The gases produced are a mixture of several silicon hydrides.
One of the gases produced in the reaction is the silicon hydride with the formula SiH4.
The structure of this molecule is similar to methane, CH4.
Draw a diagram to show the bonding in a molecule of SiH4. Represent the electrons
as dots and crosses and only show the outer shell (energy level) electrons.
(1)
Page 11 of 53
(iii)
A sample of a different silicon hydride was found to contain 1.4 g of silicon and
0.15 g of hydrogen.
Calculate the formula of this silicon hydride. You must show all your working to gain
full marks.
Relative atomic masses: H = 1; Si = 28
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(4)
(iv)
The silicon hydrides react immediately they come into contact with oxygen in the air.
They burst into flames with a small explosion and give out energy.
Which letter, A to H, best describes this reaction?
Energy involved in breaking and
forming bonds
The energy released from forming new
bonds is greater than the energy needed
to break existing bonds
Activation
energy
high
low
The energy needed to break existing bonds
is greater than the energy released from
forming new bonds
high
low
Rate of
reaction
Letter
fast
A
slow
B
fast
C
slow
D
fast
E
slow
F
fast
G
slow
H
Letter ...................
(1)
Page 12 of 53
(c)
The structure of silicon is similar to the structure of diamond.
Describe the structure of silicon and explain why it has a high melting point. You may draw
a diagram if this helps.
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(4)
(Total 15 marks)
Q8.
In 1916, during the First World War, a German U-boat sank a Swedish ship which was
carrying a cargo of champagne. The wreck was discovered in 1997 and the champagne was
brought to the surface and analysed.
(a)
25.0 cm3 of the champagne were placed in a conical flask.
Describe how the volume of sodium hydroxide solution needed to react completely with
the weak acids in 25.0 cm3 of this champagne can be found by titration, using
phenolphthalein indicator.
Name any other apparatus used.
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(4)
Page 13 of 53
(b)
The acid in 25.0 cm3 of the champagne reacted completely with 13.5 cm3 of sodium
hydroxide of concentration 0.10 moles per cubic decimetre.
Calculate the concentration in moles per cubic decimetre of acid in the champagne.
Assume that 1 mole of sodium hydroxide reacts completely with 1 mole of acid.
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Concentration = ......................... moles per cubic decimetre
(2)
(c)
Is analysis by titration enough to decide whether this champagne is safe to drink?
Explain your answer.
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(1)
Page 14 of 53
(d)
The graph shows how the pH of the solution changes during this titration.
Phenolphthalein is the indicator used in this titration. It changes colour between pH 8.2 and
pH 10.0.
Methyl orange is another indicator. It changes colour between pH 3.2 and pH 4.4.
Suggest why methyl orange is not a suitable indicator for this titration.
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(2)
(Total 9 marks)
Q9.
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)
Page 15 of 53
(ii)
What is the formula of the functional group for alcohols?
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(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.
(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)
Page 16 of 53
(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)
Q10.
An advert for some crisps claims that they now contain only 30% saturated fat because
they are cooked in sunflower oil. The crisp company used bromine water to compare
percentage unsaturation of sunflower oil with four other vegetable oils, A, B, C and D.
Oil
(i)
Volume of bromine water added until
the bromine colour just remains (cm3)
Percentage
unsaturation
(%)
Test 1
Test 2
Test 3
Average
Sunflower
25.4
28.0
27.0
26.8
A
13.0
14.0
15.0
14.0
35
B
23.2
11.2
24.0
23.6
59
C
19.9
21.1
20.2
20.4
51
D
9.5
8.8
9.3
9.2
23
What is the range of percentage unsaturation for oils A, B, C and D?
Range = ................................................ %
(1)
(ii)
Describe and explain what happens to the first drops of bromine water that are added to
these oils.
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(2)
Page 17 of 53
(iii)
The average for oil B is given as 23.6 cm3.
Explain how this average has been calculated.
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(1)
(iv)
The results did not show that sunflower oil contains 30% saturated fat.
Explain why. (You will need to calculate the percentage unsaturation of sunflower oil.)
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(2)
(Total 6 marks)
Q11.
Methanol is a fuel that is used in some racing cars instead of petrol.
Methanol can be made from carbon monoxide and hydrogen. The equation for this reaction is
shown below.
CO(g)
+
2H2(g)
CH3OH(g)
The forward reaction is exothermic.
(a)
A high pressure (between 50 and 100 atmospheres) is used in this process.
Explain why the highest equilibrium yield of methanol is obtained at high pressure.
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(1)
Page 18 of 53
(b)
The temperature used in this process is about 250 °C.
It has been stated that, ‘the use of this temperature is a compromise between the
equilibrium yield of product and the rate of reaction’.
Explain this statement.
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(3)
(Total 4 marks)
Q12.
This barbecue burns propane gas.
The structure of propane is shown below.
Page 19 of 53
(a)
Complete the diagram to show how the outer energy level (shell) electrons of hydrogen
and carbon are arranged in a molecule of propane.
(1)
(b)
The graph shows how the vapour pressure of propane changes with temperature.
The vapour pressure of a liquid is the pressure of the vapour above the liquid.
(i)
Describe, as fully as you can, how the vapour pressure of propane changes with
temperature.
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(2)
Page 20 of 53
(ii)
The boiling point of a liquid is the temperature at which its vapour pressure is equal to
the air pressure above the liquid.
Use the graph to find the boiling point of propane when the air pressure is 100
kilopascals.
Boiling point ................................................... °C
(1)
(c)
Explain, in terms of molecules, why propane has a low boiling point.
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(2)
(Total 6 marks)
Q13.
This question is about the use hydrocarbons and the production of compounds from
hydrocarbons.
(a)
The equation shows a reaction involving hydrocarbons.
C8H18
→
Hydrocarbon J
C2H4
+
Hydrocarbon K
C6H14
Hydrocarbon L
Choose the correct processes from the box to complete the sentences.
combustion
(i)
hydration
thermal decomposition
polymerisation
Hydrocarbons K and L are produced by ........................................... .
(1)
(ii)
Ethanol can be produced from hydrocarbon K by .............................. .
(1)
(iii)
Describe a test to distinguish between hydrocarbons K and L and give the result of
the test.
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(2)
Page 21 of 53
(b)
Hydrocarbon J burns completely in oxygen to produce carbon dioxide and water vapour.
2 C8H18
(i)
+
25 O2
→
16 CO2
+
18 H2O
When 114g of hydrocarbon J burns completely in 400g of oxygen it produces
162g of water vapour.
What mass of carbon dioxide would be produced from burning 114g of
hydrocarbon J?
Show clearly how you work out your answer
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Answer = ................................. g
(2)
(ii)
The mass of carbon dioxide produced is greater than the 114g of hydrocarbon J
that was burned.
Explain why.
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(2)
(c)
Two different processes are used to produce ethanol.
Process 1
Process 2
Fermentation of a sugar solution by
yeast in a reaction vessel.
Reaction of ethene (from crude oil) with
steam in a reactor.
The reaction vessel has to be emptied,
cleaned and refilled every few days.
The reaction is only stopped if there is a
fault in the reactor.
The process produces a 15% ethanol
solution in water.
The process produces 100% ethanol.
(i)
Give one advantage that Process 1 has over Process 2.
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(1)
Page 22 of 53
(ii)
What advantages to a manufacturer of ethanol, does Process 2 have over
Process 1?
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(2)
(Total 11 marks)
Q14.
Crude oil is the source of many useful materials. Crude oil is separated into fractions by
fractional distillation.
(a)
Describe how the naphtha fraction separates from the other fractions.
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(2)
(b)
The naphtha fraction is often used to make other useful materials.
This involves the cracking of hydrocarbons in the naphtha fraction.
For example:
decane
→
hexane
+
ethene
C10H22
→
C6H14
+
C2H4
Page 23 of 53
(i)
Balance the symbol equation given above.
(1)
(ii)
Describe how cracking is carried out.
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(2)
(iii)
Why does ethene have different chemical properties from decane and hexane?
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(2)
(c)
Ethene is used as the starting material for many polymers. The most common polymer is
poly(ethene). One hydrocarbon molecule in poly(ethene) will contain thousands of carbon
atoms.
Complete the diagram to show the bonds in ethene.
H
C
H
H
C
H
(1)
Page 24 of 53
(d)
Read the following information.
Landfill, Incineration, Recycling and Re-use of Poly(ethene)
People could be encouraged to re-use their poly(ethene) bags and
containers.
Recycling poly(ethene) saves raw materials and energy needed to make new
plastic. When polymers are recycled the plastics must be collected,
transported, sorted into different types by hand and washed. This requires the
use of fossil fuels and is expensive.
Poly(ethene) can be burnt in an incinerator with other household waste. The
heat released could be used to make steam to drive an electric generator.
Surplus heat could be used to heat greenhouses used for growing
vegetables. Incineration at too low a temperature can produce harmful
substances. The residue (ash) has to go to landfill.
Landfill is probably the easiest way to dispose of polymers and it is cheap.
Polymers are often mixed in with other household rubbish. Household waste
does not get sorted into different materials because it is disposed of in the
same hole in the ground. When the hole is eventually full, the waste is
covered by a layer of soil to stop it smelling. The waste gets compressed
under its own weight. Most polymers, such as poly(ethene), are not
biodegradable so will remain in the ground forever.
You are asked to decide which option for the disposal of poly(ethene) will be put forward in
your area. You decide that recycling is the best option.
Suggest one economic argument and one environmental argument that will be made
against recycling.
Page 25 of 53
For each argument made, how will you persuade those making the argument to accept
your option?
(You must use only one sentence for each argument made against your decision and only
one sentence for your response to it.)
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(4)
(Total 12 marks)
Q15.
Since 2000 there has been a lot more research into alternative, environmentally-friendly
fuels for road transport.
Several pollutants are found in the exhaust emissions produced when fossil fuels are used for
road transport.
Carbon monoxide (CO) interferes with the way that red blood cells carry oxygen. Carbon dioxide
(CO2) increases the level of carbon dioxide in the atmosphere and causes global warming.
Oxides of nitrogen (NOx) are produced at high temperatures when nitrogen and oxygen from the
atmosphere combine.
Sulfur dioxide (SO2) is produced when sulfur impurities in the fuel combine with oxygen in the
atmosphere.
Tiny particles of solids are produced when the fuel does not burn completely.
This increases the level of particulates (PM10) in the atmosphere.
(a)
Name the environmental effect caused by:
(i)
oxides of nitrogen (NOx) and sulfur dioxide (SO2)
..........................................................................................................................
(1)
(ii)
the increased level of particulates (PM10).
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(1)
Page 26 of 53
(b)
Diesel obtained from crude oil is often called fossil diesel. Biodiesel can be made from
many vegetable oils. One research project compared the exhaust emissions when fossil
diesel or biodiesel were used as fuels.
Some of the relative amounts of these exhaust emissions are shown in the bar chart.
(i)
Use your knowledge and the information above to explain the environmental benefits
of using biodiesel as a sustainable, low pollution fuel.
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(3)
Page 27 of 53
(ii)
Biodiesel is called a green fuel.
This is because the life-cycle emission of carbon dioxide from biodiesel is less than
that from fossil diesel.
Use your knowledge and the information above to explain why biodiesel’s contribution
to global warming is considered to be much less than that of fossil diesel.
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(3)
(Total 8 marks)
Q16.
An advert for crisps claimed that they are healthier because they are cooked in sunflower
oil.
(a)
A student found the following information about four oils that are used to make crisps.
Rapeseed oil
Sunflower oil
Olive oil
Corn oil
Saturated fat (%)
6.6
12.0
14.3
14.4
Polyunsaturated fat
(%)
29.3
63.3
8.2
51.3
+5
–18
–12
–15
Melting point (°C)
One hypothesis is that oils are thought to be healthier if they are:
•
low in saturated fat
•
high in polyunsaturated fat.
(i)
Use the table to decide which oil should be healthiest. Explain your decision by
comparing this oil with other oils from the table that you think are less healthy.
Healthiest oil is .....................................................................................
Explanation ...........................................................................................
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(2)
Page 28 of 53
(ii)
These oils can be hardened by reacting them with hydrogen.
A student said that hardening would make sunflower oil healthier.
Is this student’s claim correct?
Explain your answer.
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(2)
(b)
A mixture of the olive oil, water and egg yolk was shaken and left to stand. The olive oil and
water do not separate.
The diagram shows a simple model of how a stable mixture of olive oil and water is
produced by the addition of egg yolk.
Use this simple model to explain how the molecules in the egg yolk are able to produce a
stable mixture of olive oil and water.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)
(Total 7 marks)
Page 29 of 53
Q17.
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 30 of 53
Q18.
An airship caught fire when it was coming in to land in 1937. The airship was filled with
hydrogen. A spark or flame ignited the hydrogen. The hydrogen reacted with oxygen in the air to
produce water.
(a)
The equation for the reaction can be represented using structural formulae for the
chemicals.
2H–H+O=O→2H–O–H
Use the bond energies given in the table to help you to calculate the energy change for this
reaction.
Bond
Bond energy in kJ per mole
H–H
436
O=O
498
O–H
464
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
Energy change = ................................... kJ
(3)
(b)
Explain, in terms of making and breaking bonds, why this reaction is exothermic.
.....................................................................................................................................
.....................................................................................................................................
(1)
Page 31 of 53
(c)
Use the energy level diagram for this reaction to help you to answer these questions.
(i)
The hydrogen did not burn until ignited by a spark or flame.
Explain why.
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Platinum, a transition metal, causes hydrogen to ignite without using a spark or
flame.
Explain why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(Total 7 marks)
Q19.
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
Page 32 of 53
(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 33 of 53
(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=O
498
C –– O
805
O –– H
464
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
Energy change = ...................................... kJ
(3)
(ii)
In terms of the bond energies, explain why this reaction is exothermic.
..........................................................................................................................
..........................................................................................................................
(1)
(Total 6 marks)
Q20.
Sodium chloride solution is a useful raw material for the manufacture of other substances.
Page 34 of 53
(i)
What is the name of the process shown?
.....................................................................................................................................
(1)
(ii)
Chloride ions lose electrons at the positive electrode. What is the name of this type of
reaction?
.....................................................................................................................................
(1)
(iii)
The solution formed at X is alkaline. What causes this solution to be alkaline?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(iv)
Give a balanced ionic equation for the formation of hydrogen gas at the negative electrode.
.....................................................................................................................................
(3)
(Total 7 marks)
Page 35 of 53
Q21.
Magnesium reacts with dilute sulphuric acid.
magnesium + sulphuric acid → magnesium sulphate + hydrogen
A student measured the volume of hydrogen given off every 10 seconds. The results are shown
on the graph.
(a)
The average rate of hydrogen production in the first 10 seconds is
(60 cm3 ÷ 10 s) = 6 cm3/s.
(i)
Calculate the average rate of production of hydrogen between 30 seconds and 50
seconds. Show clearly how you work out your answer.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
Rate ............................... cm3/s
(3)
(ii)
Explain, as fully as you can, why the average rate between 30 and 50 seconds is
different from the rate between 0 and 10 seconds.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
Page 36 of 53
(b)
In industry, enzymes are used in both batch processes and continuous processes.
Give one reason why continuous processes are usually more profitable than batch
processes.
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 6 marks)
Q22.
This article appeared in a newspaper.
(a)
The balanced chemical equation shows the reaction between steel and hydrochloric acid.
Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g)
(i)
Which metal in steel reacted with the hydrochloric acid?
...........................................................................................................................
(1)
(ii)
The gas released was described as explosive. Explain why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
Page 37 of 53
(b)
In the factory hydrogen chloride is manufactured by reacting hydrogen with chlorine.
Hydrochloric acid is formed when hydrogen chloride forms a solution in water.
(i)
Water was sprayed on the steel and hydrochloric acid. This slowed the rate of
reaction. Explain why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(ii)
It would have been better to neutralise the acid with an alkali rather than to just add
water. Hydrochloric acid can be neutralised by reaction with sodium hydroxide.
Complete the ionic equation for the neutralisation reaction.
(aq) + (aq) → H2O(l)
(2)
(iii)
In the factory the acid leak was neutralised with slaked lime, Ca(OH)2, and not
sodium hydroxide, NaOH. Suggest why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(Total 10 marks)
Q23.
(a)
This label has been taken from a packet of Andrews Antacid.
Page 38 of 53
(i)
Write the simplest ionic equation which represents a neutralisation reaction.
...........................................................................................................................
(1)
(ii)
Chewing the tablet cures indigestion faster than swallowing the tablet whole. Explain
why.
...........................................................................................................................
...........................................................................................................................
(1)
(iii)
Write the formula of the magnesium compound present in Andrews Antacid.
You may find the Data Sheet helpful.
...........................................................................................................................
(1)
(b)
The active ingredients in the Antacid react with hydrochloric acid in the stomach to give
salts, water and carbon dioxide.
A student investigated how quickly the tablets react with excess hydrochloric acid.
40 cm³ of dilute hydrochloric acid were placed in a conical flask. The flask was placed on
a direct reading balance. Two Antacid tablets were quickly added to the flask. The
apparatus was weighed immediately. At the same time, a stop clock was started. The
mass was recorded every half minute for 5 minutes.
The results are shown in the table below.
The main active ingredient in Andrews Antacid is calcium carbonate.
(i)
Balance the equation which represents the reaction between calcium carbonate and
hydrochloric acid.
CaCO3(s) + .......... HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
(1)
(ii)
State the meaning of the symbol “(aq)”.
...........................................................................................................................
(1)
(iii)
Why does the mass of the flask and contents decrease?
...........................................................................................................................
(1)
Page 39 of 53
(c)
(i)
Plot the results on the graph below and draw a smooth curve to show how the mass
of the flask and its contents changes with time. Label this curve “A”.
(3)
(ii)
One of the results does not appear to fit the pattern. Circle this result on the graph.
(1)
(d)
The student did a second experiment. The only change was that the acid was twice as
concentrated.
On the graph, sketch a second curve to show a possible result for this experiment. Label
this curve “B”.
(2)
(Total 12 marks)
Page 40 of 53
Q24.
Limestone contains calcium carbonate, CaCO3.
At a cement works, limestone is mixed with clay and heated in a kiln.
(a)
(i)
When methane is burned in this process the waste gases contain carbon dioxide
and nitrogen.
Explain why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(ii)
Complete the symbol equation for the thermal decomposition of calcium carbonate.
CaCO3 → .........................
+
.........................
(2)
(b)
A different fuel is burnt at the cement works.
Suggest one reason the company may give for using this different fuel at the cement
works.
.....................................................................................................................................
.....................................................................................................................................
(1)
Page 41 of 53
(c)
The cement works continue to burn the different fuel.
Local residents are concerned because more children are suffering asthma attacks.
Residents have also noticed that parked cars are becoming dirty because of smoke
particles from the chimney.
The table shows the possible medical risk from smoke particles.
Particle size in mm
Medical effect
Larger than 0.4
No medical risks known
0.3 and smaller
Causes asthma attacks
0.2 and smaller
May cause cancer
It is also recommended that to avoid damage to health, the concentration of any particles
should be no higher than 2 parts per million (ppm).
Scientists were brought in to monitor the emissions from the cement work’s chimney.
They positioned four sensors around the cement works to monitor airborne smoke
particles.
These four sensors only detect particle sizes larger than 0.5 mm and measure the
concentration of particles in ppm. The scientists reported that the particle sensors showed
that the average concentration of particles was 1.8 ppm. The scientists concluded that
there was no risk to health.
(i)
Explain why the local residents objected to the positions of the four sensors.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(ii)
What evidence did the scientists use to conclude that there was no risk to health?
...........................................................................................................................
...........................................................................................................................
(1)
Page 42 of 53
(iii)
The local residents were still concerned that there was a risk to health, even though
the average concentration of particles was 1.8 ppm.
Explain why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(Total 11 marks)
Q25.
The demand for iron and steel is high.
(a)
Iron that is extracted from its oxide by carbon reduction in a blast furnace is called cast
iron. Cast iron contains about 4% carbon. This carbon makes cast iron very brittle.
Carbon steels can be made by the following processes.
• Blowing oxygen into molten cast iron to remove most of the carbon.
• Adding a calculated amount of carbon.
Sometimes different metals may also be added to the molten carbon steels.
(i)
Suggest how blowing oxygen into molten cast iron removes most of the carbon.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
Page 43 of 53
(ii)
Why are different metals sometimes added to molten carbon steels?
...........................................................................................................................
...........................................................................................................................
(1)
(b)
The percentage of iron and steel recycled in the UK has been increasing.
Year
%iron and steel recycled
1998
25
2000
35
2002
42
2004
46
2006
57
The UK government has set targets for the percentage of iron and steel to be recycled.
In 2006 the target was exceeded.
Suggest two reasons why the UK government wants to encourage recycling of iron and
steel.
1 ..................................................................................................................................
.....................................................................................................................................
2 ..................................................................................................................................
.....................................................................................................................................
(2)
(Total 5 marks)
Q26.
Copper is found in the Earth’s crust as an ore containing copper sulfide. Large areas of
land, where this ore was once quarried, are contaminated with low percentages of copper
sulfide. Copper would be too expensive to extract from this contaminated land using the
traditional method of quarrying and then heating in a furnace.
(a)
The percentage of copper ore in the contaminated land is low.
(i)
It would be too expensive to extract from this land by the traditional method.
Explain why.
...............................................................................................................
...............................................................................................................
(1)
Page 44 of 53
(ii)
Extracting copper from this land by the traditional method would have a major
environmental impact.
Give one reason why.
...............................................................................................................
...............................................................................................................
(1)
(b)
One way to extract the copper from land that contains low percentages of copper sulfide is
by bioleaching. Bioleaching uses bacteria. The bacteria produce a solution of copper
sulfate.
It is possible to get copper from a solution of copper sulfate using scrap iron.
(i)
It is economical to use scrap iron to get copper.
Give one reason why.
...............................................................................................................
...............................................................................................................
(1)
(ii)
Why can iron be used to get copper from copper sulfate solution?
...............................................................................................................
...............................................................................................................
(1)
(c)
A new way to extract the copper from land that contains low percentages of copper sulfide
is phytomining.
Phytomining uses plants. Plants are grown on this land and absorb copper compounds
through their roots.
Page 45 of 53
(i)
Use this information to give two advantages of phytomining compared to the
traditional method.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(ii)
Use this information to suggest one disadvantage of phytomining compared to the
traditional method.
...............................................................................................................
...............................................................................................................
(1)
(Total 7 marks)
Q27.
Titanium is used in aircraft, ships and hip replacement joints. Titanium is as strong as steel
but 45% lighter, and is more resistant to acids and alkalis.
Most titanium is produced from its ore, rutile (titanium oxide), by a batch process that takes up to
17 days.
Titanium reactors produce about 1 tonne of the metal per day.
Iron blast furnaces produce about 20 000 tonnes of the metal per hour.
(a)
Give one property of titanium that makes it more useful than steel for hip replacement
joints.
....................................................................................................................................
(1)
Page 46 of 53
(b)
In the reactor magnesium is used to produce titanium. If carbon were used instead of
magnesium, no titanium would be produced.
What does this tell you about the relative reactivities of carbon, magnesium and
titanium?
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(c)
The use of titanium is limited because it is expensive.
Explain why titanium costs more than steel.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(3)
(Total 6 marks)
Q28.
An electric current was passed through dilute sulphuric acid. The apparatus used is
shown. Oxygen was formed at the anode.
(a)
What name is given to solutions which decompose when electricity is passed through
them?
.....................................................................................................................................
(1)
Page 47 of 53
(b)
The ionic equation for the reaction at the anode is:
4OH– → 2H2O + O2 + 4e–
Explain this type of reaction.
.....................................................................................................................................
.....................................................................................................................................
(2)
(c)
Write a balanced ionic equation for the reaction at the cathode.
.....................................................................................................................................
(2)
(d)
What happens to the concentration of the sulphuric acid as the electricity is passed
through it? Explain your answer.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 8 marks)
Q29.
Electrolysis can be used to remove unwanted hair from the skin.
The hair is first coated with a layer of gel containing ions in solution.
The positive electrode is connected by a patch to the skin.
The negative electrode is connected to the hair. Electricity flows through the gel and causes
electrolysis of the body fluid around the hair follicle.
Page 48 of 53
(a)
Metal wires conduct electricity to the electrodes.
Explain how metals conduct electricity.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
Explain why the gel containing ions in solution can conduct electricity.
.....................................................................................................................................
.....................................................................................................................................
(1)
(c)
The body fluid is a solution that contains sodium chloride. The electricity causes the
electrolysis of a small amount of this solution.
This solution contains hydrogen ions that move to the negative electrode.
(i)
The half equation represents the reaction at the negative electrode.
2H+
+
2e–
→
H2
Explain why this reaction is a reduction.
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
As a result of the electrolysis of sodium chloride solution, an alkali forms which kills
the hair follicle.
What is the name of this alkali? .......................................................................
(1)
(iii)
Complete the half equation for the reaction at the positive electrode.
Cl –
→
Cl2
(1)
(Total 6 marks)
Page 49 of 53
Q30.
Read the article and then answer the questions that follow.
Hydrogen fuel for cars?
Hydrogen is an excellent fuel. It can be made by the electrolysis of potassium
hydroxide solution.
Hydrogen gas can be stored under pressure in a cylinder but a leak of the gas
could cause an explosion.
It has been found that lithium nitride can absorb and then release large volumes of
hydrogen. A chemical reaction takes place between the hydrogen and the lithium
nitride. The hydrogen is held in the resulting compounds by chemical bonds.
The problem is that the rate at which hydrogen is absorbed and then released
from normal sized particles of lithium nitride is slow.
Recently scientists have made ‘nanosized’ particles of lithium nitride. These
particles absorb hydrogen in the same way as normal sized lithium nitride
particles. The ‘nanosized’ particles have the advantage that they absorb and
release the hydrogen much faster when needed in the fuel cell.
It is hoped that ‘nanosized’ particles of lithium nitride may provide a safe method
of storing hydrogen in the future.
(a)
Hydrogen is produced at the negative electrode during the electrolysis of potassium
hydroxide solution.
(i)
Why are hydrogen ions attracted to the negative electrode?
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Potassium ions are also attracted to the negative electrode.
Explain why hydrogen gas is formed but not potassium.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(1)
Page 50 of 53
(b)
Lithium nitride is made by reacting lithium with nitrogen.
Balance the equation for this reaction.
.......... Li + N2 → .......... Li3N
(1)
(c)
(i)
The equation for the reaction of lithium nitride with hydrogen is:
Li3N + 2H2
LiNH2 + 2LiH
What feature of this reaction allows the hydrogen to be released?
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Hydrogen stored in a fuel tank filled with lithium nitride would be safer in an accident
than a cylinder full of hydrogen.
Suggest and explain why.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(d)
Lithium nitride is an ionic compound which contains lithium ions (Li+) and nitride ions (N3–).
(i)
The formation of a lithium ion from a lithium atom is an oxidation reaction.
Explain why.
...........................................................................................................................
...........................................................................................................................
(1)
Page 51 of 53
(ii)
The diagram shows the electronic structure of a nitrogen atom.
Complete the diagram below to show the electronic structure of a nitride ion (N3–).
(1)
(Total 8 marks)
Page 52 of 53
Page 53 of 53