Q1.
Some students slowly add solution Y to solution X.
The graph shows what happens to the pH of the solution in the beaker as they do this.
(a)
Choose words from this list to complete the sentences below.
acidic
alkaline
neutral
At point A on the graph the solution in the beaker is ...............................................
At point B on the graph the solution in the beaker is ...............................................
At point C on the graph the solution in the beaker is ...............................................
(2)
(b)
Describe, as fully as you can, what happens to the pH of the mixture as solution Y is
slowly added.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(5)
(Total 7 marks)
Page 1 of 61
Q2.
Powdered magnesium oxide was added in 0.1 g amounts to 25 cm3 of dilute hydrochloric
acid and the mixture stirred. The powder soon reacted and disappeared, but after about 1.0 g
had been added it took some time for all the solid to react. When a total of 1.1 g of powder had
been added, some of the magnesium oxide remained at the bottom of the flask.
(a)
On the following axes draw a sketch graph to show how the pH of the liquid is likely to
change during the experiment described above. Start the graph with the pH of the acid
before any magnesium oxide is added.
(3)
(b)
A second experiment was done using magnesium oxide from the same bottle with
25 cm3 of the same hydrochloric acid.
There is no catalyst for this reaction. Suggest two ways in which the rate of this reaction
could have been speeded up.
...................................................................................................................................
...................................................................................................................................
(2)
(c)
(i)
What is the symbol for the oxide ion?
...........................................................................................................................
(1)
(ii)
Complete the ionic equation for the reaction between hydrogen ions and oxide ions.
................................. + ................................. → H2O
(2)
Page 2 of 61
(iii)
The experiment was repeated, but 25 cm3 of dilute sulphuric acid was used instead
of hydrochloric acid.
The concentration of the sulphuric acid was the same as the hydrochloric acid
(0.1 M).
Why was twice as much magnesium oxide needed to neutralise the sulphuric acid
completely?
...........................................................................................................................
...........................................................................................................................
(1)
(Total 9 marks)
Q3.
A solution of Y was slowly added to a solution of X. The graph shows how the pH of the
resulting solution changed.
(a)
(i)
What was the pH of solution X before any of solution Y was added?
...........................................................................................................................
(1)
(ii)
State whether solution Y was acidic, alkaline or neutral.
...........................................................................................................................
(1)
(iii)
What volume of solution Y was needed to react with all of the substance in solution
X?
.................................................................................................................... cm3
(1)
Page 3 of 61
(b)
The chemical equation shows the reaction between an acid and an alkali to form a salt and
water.
(i)
Draw a circle round the formula of the alkali.
H2SO4
+ 2KOH
→
K2SO4
+
2H2O
(1)
(ii)
What is the formula of the salt?
...........................................................................................................................
(1)
(Total 5 marks)
Q4.
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)
Page 4 of 61
(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)
Q5.
An oven cleaner solution contained sodium hydroxide. A 25.0 cm 3 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)
Page 5 of 61
(ii)
Calculate the concentration of sodium hydroxide in the oven cleaner solution in
mol/dm3.
...........................................................................................................................
Answer = ................................... mol/dm3
(2)
(Total 9 marks)
Q6.
A student carried out a titration to find the concentration of a solution of sulphuric acid. 25.0
cm of the sulphuric acid solution was neutralised exactly by 34.0 cm3 of a potassium hydroxide
solution of concentration 2.0 mol/dm3. The equation for the reaction is:
3
2KOH(aq) + H2SO4(aq) → K2SO4(aq) + 2H2O(l)
(a)
Describe the experimental procedure for the titration carried out by the student.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(b)
Calculate the number of moles of potassium hydroxide used.
.....................................................................................................................................
Number of moles = .......................................
(2)
Page 6 of 61
(c)
Calculate the concentration of the sulphuric acid in mol/dm3.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
Concentration = .................................. mol/dm3
(3)
(Total 9 marks)
Page 7 of 61
Q7.
A titration was used to find the concentration of the sulphuric acid solution in the beaker.
Stage 1 25.0 cm 3 of the sulphuric acid solution was added to a flask using a pipette.
Stage 2 A solution of an alkali was added to the acid until the solution was neutral.
The volume of the alkali was noted.
(a)
What would be the pH of the sulphuric acid solution?
.....................................................................................................................................
(1)
(b)
Why was a pipette used instead of a measuring cylinder in Stage 1?
.....................................................................................................................................
(1)
Page 8 of 61
(c)
Name the apparatus labelled X which is used to add the alkali in Stage 2.
.....................................................................................................................................
(1)
(d)
Name an alkali that could be used in Stage 2.
.....................................................................................................................................
(1)
(e)
(i)
Name an indicator that you could use to find out when the solution was neutral.
...........................................................................................................................
(1)
(ii)
How would you know that the solution was neutral?
...........................................................................................................................
(1)
(Total 6 marks)
Page 9 of 61
Q8.
Chemical tests can be used to identify compounds.
The table shows the results of some tests carried out on three solutions, A, B and C.
Solution
Flame Test
A
Yellow
B
Brick-red
C
Hydrochloric
acid
is added
Sodium
hydroxide
solution
is added
Silver nitrate
solution
is added
Carbon
dioxide gas
produced
White
precipitate
insoluble in
excess
sodium
hydroxide
solution
White
precipitate
Dark green
precipitate
Use the information in the table to identify solutions A, B and C.
Give the name of:
(a)
solution A; ...................................................................................................................
(2)
(b)
solution B; ...................................................................................................................
(2)
(c)
the metal ion in solution C. .........................................................................................
(1)
(Total 5 marks)
Page 10 of 61
Q9.
This label has been taken from a bottle of household ammonia solution.
Household ammonia is a dilute solution of ammonia in water. It is commonly used to remove
grease from ovens and windows.
(a)
The amount of ammonia in household ammonia can be found by titration.
25.0 cm3 of household ammonia is placed in a conical flask. Describe how the volume of
dilute nitric acid required to neutralise this amount of household ammonia can be found
accurately by titration. Name any other apparatus and materials used.
To gain full marks you should write down your ideas in good English. Put them into a
sensible order and use correct scientific words.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(4)
Page 11 of 61
(b)
In an experiment, it was found that 25.0 cm3 of household ammonia was neutralised by
20.0 cm3 of dilute nitric acid with a concentration of 0.25 moles per cubic decimetre.
The balanced symbol equation which represents this reaction is
NH3(aq) + HNO3(aq) → NH4NO3(aq)
Calculate the concentration of the ammonia in this household ammonia in moles per cubic
decimetre.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
Concentration = ............................. moles per cubic decimetre
(2)
(c)
The salt, ammonium nitrate, is formed in this reaction.
Describe, and give the result of, a chemical test which shows that ammonium nitrate
contains ammonium ions.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(Total 8 marks)
Page 12 of 61
Q10.
Chemical tests can be used to identify compounds.
(a)
List A gives the names of four compounds in solution. List B gives tests and the result of
the tests.
Draw a straight line from each compound in List A to its test and test result in List B. The
first one has been done for you.
(2)
(b)
State what you would see when sodium hydroxide solution reacts with copper sulphate
solution.
....................................................................................................................................
....................................................................................................................................
(2)
(Total 4 marks)
Page 13 of 61
Q11.
(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 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);
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
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 14 of 61
(b)
The flow diagram shows some reactions of ethanoic acid.
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 15 of 61
Q12.
Four labels have come off four bottles.
Describe and give the results of the chemical tests that you would do to identify which bottle
contained which substance.
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
................................................................................................................................................
(Total 5 marks)
Q13.
Chemical tests are used to identify compounds.
(a)
What colour is produced by sodium compounds in flame tests?
.....................................................................................................................................
(1)
Page 16 of 61
(b)
Chemical tests are carried out on these substances.
ammonium
copper bromide
potassium nitrate
copper nitrate
magnesium sulphate
zinc carbonate
Complete each sentence by choosing the correct substance from the box. You may use
each substance once or not at all.
The substance which
(i)
reacts with dilute hydrochloric acid to produce carbon dioxide gas is
............................................................................................................................
(1)
(ii)
in solution reacts with sodium hydroxide solution to form a blue precipitate is
...........................................................................................................................
(1)
(iii)
in solution reacts with barium chloride solution, in the presence of dilute hydrochloric
acid, to form a white precipitate is
............................................................................................................................
(1)
(c)
State what you see when sodium chloride solution reacts with silver nitrate solution in the
presence of dilute nitric acid.
......................................................................................................................................
(1)
(Total 5 marks)
Q14.
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)
Page 17 of 61
(b)
Test and result for carbonate ions
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(Total 4 marks)
Q15.
Tennis players sometimes use smelling salts to help revive them.
The active chemical in smelling salts is ammonium carbonate, (NH4)2CO3.
A student tested some smelling salts to prove that they contained ammonium ions and
carbonate ions.
(a)
Complete these sentences by choosing the correct substances from the box.
(i)
Test for carbonate ions.
ammonia
carbon dioxide
limewater
hydrochloric acid
water
The student added ......................................................... to the smelling salts.
A gas called ......................................................... was given off.
This gas turned ......................................................... milky.
(3)
(ii)
Test for ammonium ions.
ammonia
carbon dioxide
acid
litmus
hydrochloric
sodium hydroxide
The student added ......................................................... to the smelling salts.
A gas called ......................................................... was given off.
This gas turned ......................................................... paper blue.
(3)
Page 18 of 61
(b)
Suggest why ammonium ions cannot be identified using a flame test.
....................................................................................................................................
....................................................................................................................................
(1)
(Total 7 marks)
Q16.
(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.
Page 19 of 61
(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:
...........................................................................................................................
...........................................................................................................................
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)
(Total 8 marks)
Page 20 of 61
Q17.
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.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(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.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
Concentration = ......................... moles per cubic decimetre
(2)
(c)
Is analysis by titration enough to decide whether this champagne is safe to drink?
Explain your answer.
.....................................................................................................................................
.....................................................................................................................................
(1)
Page 21 of 61
(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.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 9 marks)
Page 22 of 61
Q18.
In 1916 a ship was sunk by a German submarine. The ship was carrying bottles of
champagne. The wreck was discovered in 1997 and the champagne was brought to the surface
and analysed.
The diagram shows the apparatus used to find the amount of acid in 25 cm3 of the champagne.
(a)
Choose the correct words from the box to name apparatus X and Y.
beaker
cylinder
(i)
burette
conical flask
measuring
Apparatus X is a ................................................................................................
(1)
(ii)
Apparatus Y is a ................................................................................................
(1)
(b)
Sodium hydroxide solution was added to this champagne until substance Z showed that
the reaction was complete. The volume of sodium hydroxide used was recorded. The
result was used to calculate the amount of acid present.
Complete these sentences by drawing a ring around the correct answer.
a catalyst
(i)
Substance Z is
a conductor
an indicator
(1)
Page 23 of 61
changed colour
(ii)
The reaction was complete when substance Z
formed a gas
gave a precipitate
(1)
distillation
(iii)
The name of this method of analysis is
filtration
titration
(1)
(c)
250 cm3 of this champagne were found to contain 1 g of acid.
Calculate the mass of acid in 750 cm3 of this champagne.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
Mass = .......................................... g
(2)
(d)
(i)
Which one of the following ions makes champagne acidic?
Draw a ring around your answer.
chloride
hydrogen
sodium
(1)
(ii)
The acid in champagne is a weak acid.
Complete this sentence by drawing a ring around the correct answer.
has a low boiling point
The word weak means that the acid
is dilute
is partially ionised
(1)
(Total 9 marks)
Page 24 of 61
Q19.
A bottle of washing soda was found in a school laboratory. The modern name of washing
soda is sodium carbonate.
A student tested the washing soda to prove that it was sodium carbonate.
(a)
The student did a flame test to show that washing soda is a sodium compound.
The student used a clean wire to put the washing soda into the flame.
(i)
Why should the wire be clean when used for a flame test?
............................................................................................................................
(1)
(ii)
The table shows some properties of metals.
Two of these are properties that the wire must have if it is used for a flame test.
Put a tick ( ) next to the two correct properties.
Property
( )
Good electrical
conductor
High density
High melting point
Low boiling point
Unreactive
(2)
(iii)
Which one of the following flame colours shows that washing soda is a sodium
compound?
Draw a ring around your answer.
brick-red
lilac
yellow-orange
(1)
Page 25 of 61
(b)
The student used dilute hydrochloric acid to show that washing soda was a carbonate.
Carbon dioxide gas was given off.
(i)
Describe what you see happening when a gas is given off.
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
The student used limewater to prove that the gas given off was carbon dioxide.
Complete this sentence by choosing the correct word from the box.
clear
colourless
milky
When carbon dioxide reacts with limewater, the limewater turns
.....................................................
(1)
(c)
Instrumental methods are used to identify chemicals.
Describe some advantages of instrumental methods compared with chemical tests by
considering:
•
•
the length of time needed to carry out a test
the amount of chemical used.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 8 marks)
Q20.
Chlorine and bromine are important Group 7 elements.
(a)
Explain why chlorine is added to drinking water.
.....................................................................................................................................
.....................................................................................................................................
(1)
Page 26 of 61
(b)
Describe what you would see when bromine water is added to an unsaturated organic
compound.
.....................................................................................................................................
.....................................................................................................................................
(1)
(c)
Bromine can be extracted from seawater. The dissolved bromide ions are reacted with
chlorine. Bromine and chloride ions are formed.
(i)
Complete and balance the equation below, which represents the reaction between
chlorine and bromide ions.
Cl2 + 2Br– → ......................... + .........................
(1)
(ii)
Describe what you see when chlorine is added to a solution containing bromide ions.
...........................................................................................................................
...........................................................................................................................
(1)
(d)
In terms of electronic structure:
(i)
state why bromine and chlorine are both in Group 7
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
explain why bromine is less reactive than chlorine.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
Page 27 of 61
(e)
What is the result of adding acidified silver nitrate solution to a solution containing:
(i)
chloride ions
...........................................................................................................................
(1)
(ii)
bromide ions?
...........................................................................................................................
(1)
(Total 10 marks)
Q21.
This label has been taken from a packet of My Baby Food.
MY BABY FOOD
Infant milk
Pure and natural
Closest to mothers’ breast milk
Contains traces of essential minerals
500 g
One of the minerals in My Baby Food is calcium carbonate, CaCO3.
(a)
Chemical tests are used to identify elements and compounds.
(i)
A flame test can be used to identify calcium ions.
What colour do calcium ions give in a flame test?
...........................................................................................................................
(1)
(ii)
When a flame test was carried out on My Baby Food, the presence of calcium ions
was not seen. A yellow flame was produced.
Name the ion which gives a yellow flame test.
...........................................................................................................................
(1)
Page 28 of 61
(iii)
Suggest one advantage of using an instrumental method to detect the elements
present in My Baby Food.
...........................................................................................................................
...........................................................................................................................
(1)
(iv)
Name an instrumental method for detecting elements.
...........................................................................................................................
(1)
(b)
Read the information in the box below and then answer the question.
Calcium carbonate occurs naturally as marble and limestone. They are
important building materials and are often used for gravestones.
Calcium carbonate is also an essential mineral for good health and is
present in many baby foods in small amounts.
My Baby Food is recommended as being the closest to a mother’s own
breast milk. It is given free to mothers in the developing world – without it
their babies might die of malnutrition.
Responsible Mothers Are Us (RMAU) is a United Kingdom pressure group.
They want to ban chemicals in baby foods. The group was founded by Mrs I.
M. Right who has made a career in ‘goodness’ and is paid from donations
given to RMAU by members of the public.
When interviewed, she said: “Calcium carbonate is a chemical and so it is a
pollutant. My Baby Food must be banned to prevent the mass medication of
babies. I don’t feed my baby the stuff of gravestones.”
Many people do not agree with Mrs Right’s ideas.
Suggest why.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 7 marks)
Page 29 of 61
Q22.
Supreme is used to clean and degrease tiles, work surfaces and windows. The active ingredient
is ammonia solution, which is an alkali.
(a)
Draw a ring around the correct answer to complete these sentences.
hydroxide
(i)
Ammonia solution is alkaline because of
magnesium
ions.
sulfate
(1)
blue.
(ii)
Ammonia solution turns litmus paper
green.
red.
(1)
(b)
The diagram shows the apparatus a student could use for a titration.
Page 30 of 61
Draw a ring around the correct answer to complete each sentence about how the student
could do this titration.
pipette.
(i)
Measure 25 cm3 of Supreme into a conical flask using a
test tube.
thermometer.
(1)
(ii)
Add a few drops of an indicator to the Supreme in the conical flask.
beaker.
Then put hydrochloric acid into a
burette.
measuring cylinder.
(1)
changes colour.
(iii)
Add the acid to the Supreme until the indicator
dissolves.
forms a gas.
(1)
(c)
The student recorded the volume of hydrochloric acid used.
Suggest how the student could check the reliability of this result.
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 6 marks)
Page 31 of 61
Q23.
Chemical tests can be used to identify ions in solutions.
(a)
List A gives the names of two sulfates in solution.
List B gives the results of adding sodium hydroxide solution.
Draw a straight line from each sulfate in List A to its correct test result in List B.
List A
Name of sulfate
in solution
List B
Result of adding
sodium hydroxide solution
(2)
(b)
Suggest why clean test tubes were used for each test.
.....................................................................................................................................
.....................................................................................................................................
(1)
(c)
Draw a ring around the correct colour to complete this sentence.
Sulfate solutions react with barium chloride solution to give a
blue
green
precipitate.
white
(1)
(Total 4 marks)
Page 32 of 61
Q24.
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.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(2)
(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)
Page 33 of 61
(b)
Read the following information and then answer the questions.
Salt – friend or foe?
Sodium chloride (salt) is an essential mineral for our health. It is used to flavour
and preserve foods. Too much sodium in our diet may increase the risk of high
blood pressure and heart disease. Heart disease is the biggest cause of death in
the United Kingdom. Some people claim that excess sodium is a poison that can
cause cancer, while others say that more evidence is needed.
Many processed foods contain salt, so it is easy to exceed the recommended
daily upper limit of about 5 g of salt per person. A ‘healthier’ amount should be
about 3 g. In the United Kingdom many people consume over 10 g of salt each
day.
One way to reduce sodium in our diet is to use Low Sodium Salt. This has two
thirds of the sodium chloride replaced by potassium chloride.
A national newspaper asked readers for their views on two options.
Option 1: Ban the use of sodium chloride in foods.
Option 2: Reduce the amount of sodium chloride in all foods to a ‘healthier’ level.
(i)
Suggest why Option 1 was rejected.
...........................................................................................................................
...........................................................................................................................
(1)
(ii)
Suggest two advantages and one disadvantage of Option 2.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(Total 8 marks)
Page 34 of 61
Q25.
The use of too much common salt (sodium chloride) in our diet increases the risk of heart
problems. One way to reduce sodium chloride in our diet is to use Low Sodium Salt instead of
common salt.
A student tested Low Sodium Salt to find out if it contained both potassium chloride and sodium
chloride and what ions were in the anti-caking agent.
(a)
The student did a flame test.
The flame colour showed that there were sodium ions in the Low Sodium Salt.
The student did not observe the colour in the flame which would show that there were
potassium ions in the Low Sodium Salt.
Suggest why.
(You will need to state the flame colours of sodium ions and potassium ions in your
answer.)
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)
(b)
The student did a test to find which metal ion was in the anti-caking compound.
The student had not seen any red colour in the flame while doing the flame test.
The student added water to make a solution of Low Sodium Salt.
The student then added sodium hydroxide solution. A white precipitate formed that was
insoluble in excess sodium hydroxide solution.
Use the information to draw a ring around the name of the metal ion that is in the anticaking agent.
aluminium
calcium
magnesium
(1)
Page 35 of 61
(c)
A student was provided with the following reagents to test for non-metal ions in the Low
Sodium Salt.
•
•
•
•
Calcium hydroxide solution
Dilute hydrochloric acid
Silver nitrate in solution
Dilute nitric acid
The table shows the tests that student did and the observations that the student made.
Tests
Observations
Dilute nitric acid was added to Low Sodium Salt
The mixture fizzed and the gas given
off turned limewater cloudy.
Excess nitric acid was added to the Low Sodium
Salt, and then silver nitrate solution was added.
A white precipitate formed in the
solution.
(i)
From the table what conclusions can you make about the non-metal ions that are in
the Low Sodium Salt?
Explain your conclusions.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(ii)
Another student used hydrochloric acid instead of nitric acid for the tests shown in
the table.
Describe what this student would observe and explain why this student’s
conclusions would not be valid.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(3)
(Total 9 marks)
Page 36 of 61
Q26.
Drain Buster is used to clear and degrease drains. Sodium hydroxide is the main chemical
substance in Drain Buster.
(a)
A student planned an experiment to find the concentration of the sodium hydroxide solution
in Drain Buster.
The teacher had to dilute the Drain Buster before the student could use it.
Explain why.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)
Page 37 of 61
(b)
In this question you will get marks on using good English, organising information clearly
and using specialist terms where appropriate.
The student wanted to find the volume of hydrochloric acid that reacts with a known
volume of diluted Drain Buster.
Describe how the student could do this by titration.
In your description you should include:
•
the names of pieces of apparatus used
•
the names of the substances used
•
a risk assessment
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(6)
(Total 8 marks)
Q27.
The use of too much common salt (sodium chloride) in our diet increases the risk of heart
problems. One way to reduce sodium chloride in our diet is to use Low Sodium Salt instead of
common salt.
Page 38 of 61
A student tested Low Sodium Salt to find out if it contained all of the compounds on the list of
ingredients.
(a)
The student added dilute hydrochloric acid to Low Sodium Salt to show that it contains
carbonate ions. Carbon dioxide gas was given off.
(i)
What would the student see that shows a gas is given off?
...............................................................................................................
...............................................................................................................
(1)
(ii)
The student tested the gas given off to show that the gas was carbon dioxide.
Complete the sentence.
When carbon dioxide gas is mixed with limewater
the solution turns ....................................................... .
(1)
(b)
The student tested for magnesium ions. The student added sodium hydroxide solution to a
solution of Low Sodium Salt.
What is the colour of the precipitate that the student would see?
........................................................................................................................
(1)
(c)
The student did a flame test using Low Sodium Salt.
(i)
The flame colour the student saw was yellow. Which compound in Low Sodium Salt
produces this flame colour?
...............................................................................................................
(1)
(ii)
The student did not observe the colour in the flame which would show that there
were potassium ions in the Low Sodium Salt.
Suggest why.
(You will need to state the flame colour of the potassium ions in your answer.)
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(Total 6 marks)
Page 39 of 61
M1.
(a) acidic }
neutral }
alkaline}
in this order
all correct 2 marks
one correct 1 mark
2
(b)
ideas that
•
nothing happens at first (to pH) / pH stays the same
•
then (rapidly) changes / increases
•
then stays at same (higher) level
5
[7]
M2.
(a)
starts at 0 g pH below 2
1
as more magnesium oxide added
smooth curve rises to reach its
maximum between 1 g and 1.2 g
accept a straight line from the Y axis to where the ‘curve’ becomes
horizontal
1
levels out 7 ± 1 small squares
do not credit a rates of reaction shaped curve
1
(b)
heat it
do not credit catalyst or add hot acid or crushing powder
1
stir it faster or shake it
1
Page 40 of 61
(c)
(i)
O2–
1
(ii)
2H+ + O2–
1 mark for 2H+ and 1 mark for O2- no ecf
2
(iii)
formula is (H2SO4 which) has two H+ ions
accept sulphuric acid is diprotic or has two H’s
(whereas HCl only has one)
accept it has twice as many H’s as hydrochloric acid or two
balanced equations illustrating that 2 mol of magnesium oxide is
needed
1
[9]
M3.
(a)
(i)
allow a number between 2.5 and 3
(inclusive)
accept just under 3 or about 3
1
(ii)
alkaline or alkali
1
(iii)
25
ignore any reference to units
1
(b)
(i)
a circle round KOH or 2 KOH
1
(ii)
K2SO4
do not credit potassium sulphate
1
[5]
M4.
(a)
pipette / burette
1
(b)
named indicator eg methyl orange / phenolphthalein
not universal
accept litmus but not litmus paper
1
Page 41 of 61
(c)
2 for correct answer
1
= 0.01
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]
M5.
(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
Page 42 of 61
(ii)
0.02 ×
= 0.8 mol / dm3
1
allow e.c.f. ie their (c)(i) ×
1
[9]
M6.
(a)
any four from:
•
sulphuric acid measure by pipette
or diagram
•
potassium hydroxide in burette
or diagram
•
if solutions reversed, award
•
note initial reading
•
use of indicator
•
note final reading or amount used
4
(b)
1
= 0.068
1
(c)
½ or 0.5 moles H2SO4 react with 1 mole KOH
1
moles H2SO4 in 25.0 cm3 = 0.068 × 0.5
1
moles H2SO4 in 1 dm3 =
= 1.36 mol/dm3
1
[9]
Page 43 of 61
M7.
(a)
0–6
1
(b)
more accurate
1
(c)
burette
1
(d)
sodium hydroxide / potassium hydroxide / ammonia / any other soluble
Group I or II hydroxide
1
(e)
(i)
named indicator / litmus / U.I. / methyl orange / methyl red / phenolphthalein
1
(iii)
colour at end point
1
[6]
M8.
(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]
Page 44 of 61
M9.
(a)
must be a description of a titration no titration = 0 marks
Quality of written communication
for correct sequencing of 2 of first 3 bullet points i.e. 1 + 2
or 2 + 3 or 1 + 3
1
any three from:
•
nitric acid in burette
do not accept biuret
can be inferred from 3rd point
•
add nitric acid until indicator changes (colour)
can be named acid-base indicator
colour change does not have to be correct
•
note (burette) volume used or final reading
•
accuracy: e.g. repeat
accept white tile or dropwise near end or white background or
swirling the flask or read meniscus at eye level
3
(b)
e.g. formula method:
25 × MNH3 = 0.25 × 20
1
MNH3 = 0.2
correct answer alone = 2
OR
moles NH3 = moles HNO3
=
× 0.25 = 0.005 moles (1)
concentration NH3
=
= 0.2 (1)
1
Page 45 of 61
(c)
sodium hydroxide or potassium hydroxide or lithium hydroxide or calcium
hydroxide
ignore mention of alkali
1
ammonia produced
accept gas produced turns (damp) (red) litmus blue (not blue
litmus) or alkaline gas produced
any suitable named indicator e.g. UI with consequential marking
white fumes / smoke with (concentrated) HCl
do not accept white gas wrong test = 0 marks
1
[8]
M10.
(a)
all three correct = 2
one or two correct = 1
2
(b)
blue
1
precipitate
solid
1
[4]
Page 46 of 61
M11.
(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)
M 1 = 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 47 of 61
M12.
any series of chemical tests that work should be given credit
each mark is for test + result + inference
identifying all 4 substances unambiguously with no errors gains 5 marks
e.g.
•
Flame test: yellow / orange
Na+
sodium sulphate
ignore incorrect flame test colours for
other compounds
1
•
Add NaOH to remaining 3 samples:
no (white) ppt / ammonia
no need to test for ammonia
1
NH4+
ammonium sulphate (white) ppt
magnesium ions
or aluminium ions
1
•
add excess NaOH to the 2 samples which gave a (white) ppt:
ppt dissolves
aluminium sulphate
ppt insoluble
magnesium sulphate
2
or
•
Add NaOH:
no ppt: ammonia
NH4+
(1)
ammonium sulphate
the other one is sodium sulphate (1)
(damp red) litmus* goes blue
NH3
ammonium sulphate
the other one is sodium sulphate
•
Add excess NaOH to the 2 samples
which gave the white ppt (1)
ppt dissolves
aluminium sulphate (1)
ppt insoluble
magnesium sulphate (1)
(*) or UI/pH indicator goes blue/purple
[5]
Page 48 of 61
M13.
(a)
yellow / yellow orange orange
1
(b)
(i)
zinc carbonate
1
(ii)
copper bromide
1
(iii)
magnesium sulphate
1
(c)
(white) precipitate / solid
do not accept cloudy or milky
do not accept residue
green precipitate = 0
1
[5]
M14.
(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]
M15.
(a)
(i)
(hydrochloric) acid
1
carbon dioxide
1
limewater
1
Page 49 of 61
(ii)
sodium hydroxide
1
ammonia
1
litmus
1
(b)
no distinctive colour (flame) owtte
allow: not a metal (ion)
accept flame tests only identify single elements
1
[7]
##
(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
(ii)
all would give a yellow / yellow-orange
(flame) / same coloured (flame) / same results
allow orange (flame)
or
they all contain sodium owtte
1
Page 50 of 61
(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]
M17.
(a)
must be description of a titration no titration = no marks
NaOH in burette
do not accept biuret etc
1
add NaOH until (indicator) changes colour
if specific colour change mentioned, must be correct – colourless
to pink / red or ‘goes pink / red’
do not accept ‘clear’ for colourless
1
note (burette) volume used or final reading
accept ‘work out the volume’
1
one other point: eg repeat
accept:
(white) tile or add dropwise / slowly or white background or
swirling / mix or read meniscus at eye level or wash apparatus
1
Page 51 of 61
(b)
0.054
for 2 marks
(0.1 × 13.5)/25 for 1 mark
(c)
don’t know – insufficient evidence to decide
owtte
any sensible answer
or
depends on whether acid level is considered safe or unsafe
yes, safe – acid level low / weak acids / low compared with stomach acid
owtte
any sensible answer
2
no, unsafe – acid level (too) high / other substances or bacteria may be
present / insufficient evidence to decide
owtte
any sensible answer
1
(d)
(methyl orange) would have changed colour (well) before the end-point / pH7 / neutral
owtte
1
weak acid present
weak acid-strong base (titration)
allow methyl orange used for strong acid-weak base titration
1
[9]
M18.
(a)
(i)
burette
1
(ii)
conical flask
accept conical / flask
1
(b)
(i)
an indicator
1
(ii)
changed colour
1
(iii)
titration
1
(c)
3
correct answer = 2 marks
(1 × 3) or (1 × 750/250) = 1 mark
1
Page 52 of 61
(d)
(i)
hydrogen
2
(ii)
is partially ionised
1
[9]
M19.
(a)
(i)
get wrong coloured flame/result owtte
or
to get the correct result
allow contaminated
1
(ii)
high melting point
1
unreactive
1
(iii)
yellow-orange
1
(b)
(i)
bubbles / fizz / effervescence
ignore any named gas
1
(ii)
milky
1
(c)
fast(er)
1
small(er) amount
1
[8]
M20.
(a)
kills bacteria / sterilises (water)
allow kills microorganisms / microbes / germs
allow ‘makes (water) safe (to drink)’ or disinfectant
ignore cleans water or removes impurities / bacteria
1
(b)
goes colourless / decolourised (from red / red-brown / brown / yellow / orange)
allow colour disappears
ignore ‘goes clear’ or discoloured
do not accept incorrect initial colour
do not accept precipitate
1
Page 53 of 61
(c)
(i)
Br2 and 2Cl–
allow multiples / fractions if whole equation balanced
1
(ii)
changes to red / red-brown / brown / yellow / orange
do not accept effervescence / fizzing / precipitate / gas given off
ignore vapour / temperature changes / ignore initial colour
1
(d)
(i)
7 outer electrons or
same number of outer electrons
allow last / final shell for outer
allow energy level / orbit / ring for shell
allow ‘need to gain 1 e– to have a full outer shell’
ignore ‘similar number of outer electrons’
1
(ii)
bromine / it (atom) is bigger or
must be a comparison
outer electrons (level / shell) further from nucleus or more shells
do not accept more outer shells
ignore more electrons
forces / attractions are weaker or more shielding or attracts less
do not accept magnetic / gravitational / intermolecular forces
allow ‘electron(s) attracted less easily’
electron(s) gained less easily
“outer / last / final” must be mentioned once, otherwise max 2
marks.
accept converse for chlorine throughout where clearly stated
3
(e)
(i)
white precipitate or white solid
ignore names of chemicals
1
(ii)
cream precipitate or cream solid
allow pale yellow / off-white precipitate / solid
ignore names of chemicals
1
[10]
M21.
(a)
(i)
red / brick-red / orange-red / red-orange
allow red-brown or brown-red
do not accept orange alone eg ‘red or orange’ = 0
1
Page 54 of 61
(ii)
sodium
allow sodium compounds
ignore incorrect symbol
or Na / Na+
if symbol alone given do not accept Na2+ or Na–
1
(iii)
any one from
•
accurate / sensitive
•
use small amounts
•
fast / quick / rapid
•
ease of automation
•
reliable / efficient
•
operatives do not need chemical skills
ignore cost / safety / human error or ease of use or shows all the
elements
1
(iv)
(atomic absorption) spectroscopy or (mass) spectrometry
accept AAS / aas or mass spec
accept atomic absorption
ignore ms / MS
do not allow UV / IR / NMR / chromatography / GLC
1
Page 55 of 61
(b)
any three from:
•
(safe because) similar to mothers. milk
allow calcium carbonate is in breast milk
allow some mothers unable to breast feed
ignore ‘recommended’ alone
•
babies (in developing world) would die
accept causes malnutrition
•
if banned there would be a cost involved
allow it is free
•
it is not a pollutant / harmful / dangerous
accept not all chemicals are pollutants / harmful / dangerous
•
not mass medication
•
not just used for gravestones
allow it has many uses
ignore only small amounts of it or it occurs naturally
•
(calcium carbonate) is needed for bones / teeth / health
allow ‘essential mineral’
•
Mrs Right has a personal interest or not impartial or distorts
information / bias or she is paid by a charity
accept ‘it is (only) her opinion’
3
[7]
M22.
(a)
(i)
hydroxide
1
(ii)
blue
1
(b)
(i)
pipette
1
(ii)
burette
1
(iii)
changes colour
1
(c)
repeat
allow check results with another group or student
1
[6]
Page 56 of 61
(a)
M23.
copper sulfate → blue precipitate
1
iron(II) sulfate → green precipitate
1
(b)
eg some idea of contamination
allow so you can see the colour change clearly / easily
or
give misleading / incorrect results / lead to wrong conclusion
allow to get accurate / reliable results
ignore fair test
1
(c)
white
1
[4]
M24.
(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
Page 57 of 61
(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
•
(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]
M25.
(a)
sodium – yellow flame
1
potassium – lilac flame
1
potassium’s flame colour is masked by sodium’s flame colour
1
Page 58 of 61
(b)
magnesium
1
(c)
(i)
carbonate (ions) must be present because carbon
dioxide was produced when nitric acid was added
1
chloride (ions) must be present because a white precipitate
formed when acidified silver nitrate solution was added
1
(ii)
the student would make the same observations using
either hydrochloric acid or nitric acid
1
any conclusion would not be valid because hydrochloric
acid contains chloride (ions)
1
the explanation is that these chloride (ions) would cause
a white precipitate without the presence of the low
sodium salt / sodium chloride / potassium chloride
1
[9]
M26.
(a) Drain Buster is a concentrated sodium hydroxide solution
that would damage the skin
1
therefore it is diluted so that it is safe to use for the experiment
1
(b)
Marks awarded for this answer will be determined by the Quality
of Written Communication (QWC) as well as the standard of the
scientific response.
No relevant content.
0 marks
There is a brief description of the titration that may include a
risk assessment.
Level 1 (1–2 marks)
There is some description of the titration that may include a
risk assessment.
Level 2 (3–4 marks)
There is a clear, balanced and detailed description of the
titration and an appropriate risk assessment.
Level 3 (5–6 marks)
Page 59 of 61
examples of the chemistry points made in the response
•
burette / acid / HCl used correctly
•
pipette used for Drain Buster solution / alkali / NaOH correctly
•
read meniscus at eye level
•
acid / HCl added dropwise
•
indicator used
•
white background/tile
•
end-point of titration recorded
•
swirling/mixing
•
repeat
example of risk assessment points made in the response eg
•
Wear safety goggles – to protect eyes because
hydrochloric acid is corrosive / irritant and / or
sodium hydroxide is caustic
[8]
M27.
(a)
(i)
fizzing / effervescing
1
(ii)
cloudy / milky / white
1
(b)
white
1
(c)
(i)
sodium chloride
1
(ii)
potassium ions give a lilac flame colour
1
potassium’s flame colour is masked by sodium’s flame colour
1
[6]
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