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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.
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(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.
H2SO
4 + 2KOH → K
2SO
4 + 2H
2O
(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
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.....................................................................................................................................
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Concentration of hydrochloric acid = ........................................ mol/dm3
(2) (Total 6 marks)
Q5. An oven cleaner solution contained sodium hydroxide. A 25.0 cm3 sample of the oven cleaner solution was placed in a flask. The sample was titrated with hydrochloric acid containing 73 g/dm3 of hydrogen chloride, HCI.
(a) Describe how this titration is carried out.
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.....................................................................................................................................
..................................................................................................................................... (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
cm3 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:
2KOH(aq) + H2SO
4(aq) → K
2SO
4(aq) + 2H
2O(l)
(a) Describe the experimental procedure for the titration carried out by the student.
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..................................................................................................................................... (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.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
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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 cm3 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.
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)
Solution Flame Test Hydrochloric
acid is added
Sodium hydroxide solution is added
Silver nitrate solution is added
A Yellow
Carbon dioxide gas produced
B Brick-red White precipitate insoluble in
excess sodium
hydroxide solution
White precipitate
C
Dark green precipitate
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.
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(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) + HNO
3(aq) → NH
4NO
3(aq)
Calculate the concentration of the ammonia in this household ammonia in moles per cubic decimetre.
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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.
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.................................................................................................................................... (2)
(Total 8 marks)
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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.
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.................................................................................................................................... (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 cm3 sample of
vinegar was neutralised by 45.000 cm3 of sodium hydroxide solution, of concentration 0.20 moles per cubic decimetre (moles per litre).
The equation which represents this reaction is
CH3COOH + NaOH → CH
3COONa + H
2O
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)
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.
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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 magnesium sulphate
potassium nitrate copper nitrate 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)
2CO
3.
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
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.................................................................................................................................... (2)
Page 17 of 61
(b) Test and result for carbonate ions
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.................................................................................................................................... (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)
2CO
3.
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.
The student added ......................................................... to the smelling salts.
A gas called ......................................................... was given off.
This gas turned ......................................................... milky. (3)
ammonia carbon dioxide hydrochloric acid
limewater water
(ii) Test for ammonium ions.
The student added ......................................................... to the smelling salts.
A gas called ......................................................... was given off.
This gas turned ......................................................... paper blue. (3)
ammonia carbon dioxide hydrochloric acid
litmus sodium hydroxide
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:
...........................................................................................................................
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Test and result for chloride ions:
...........................................................................................................................
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Test and result for nitrate ions:
...........................................................................................................................
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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.
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(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.
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(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.
.....................................................................................................................................
..................................................................................................................................... (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.
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(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.
(i) Apparatus X is a ................................................................................................ (1)
beaker burette conical flask measuring cylinder
(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.
(1)
(i) Substance Z is
a catalyst
a conductor
an indicator
Page 23 of 61
(1)
(ii) The reaction was complete when substance Z
changed colour
formed a gas
gave a precipitate
(1)
(iii) The name of this method of analysis is
distillation
filtration
titration
(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.
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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.
(1) (Total 9 marks)
The word weak means that the acid
has a low boiling point
is dilute
is partially ionised
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.
(2)
Property ( )
Good electrical conductor
High density
High melting point
Low boiling point
Unreactive
(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.
When carbon dioxide reacts with limewater, the limewater turns
..................................................... (1)
clear colourless milky
(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.
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(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
...........................................................................................................................
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(ii) explain why bromine is less reactive than chlorine.
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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.
One of the minerals in My Baby Food is calcium carbonate, CaCO3.
MY BABY FOOD
Infant milk Pure and natural
Closest to mothers’ breast milk Contains traces of essential minerals
500 g
(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.
Many people do not agree with Mrs Right’s ideas.
Suggest why.
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(Total 7 marks)
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.”
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.
(1)
(i) Ammonia solution is alkaline because of
hydroxide
magnesium
sulfate
ions.
(1)
(ii) Ammonia solution turns litmus paper
blue.
green.
red.
(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.
(1)
(i) Measure 25 cm3 of Supreme into a conical flask using a
pipette.
test tube.
thermometer.
(ii) Add a few drops of an indicator to the Supreme in the conical flask.
(1)
Then put hydrochloric acid into a
beaker.
burette.
measuring cylinder.
(1)
(iii) Add the acid to the Supreme until the indicator
changes colour.
dissolves.
forms a gas.
(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 List B Name of sulfate Result of adding in solution 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
(1) (Total 4 marks)
blue
green
white
precipitate.
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.
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........................................................................................................................... (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.
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(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.)
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(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 anti-caking agent.
aluminium calcium magnesium (1)
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(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)
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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)
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(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.
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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)
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M1. (a) acidic } neutral } in this order alkaline}
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
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(c) (i) O2–
1
(ii) 2H+ + O2–
1 mark for 2H+ and 1 mark for O2- no ecf
2
(iii) formula is (H2SO
4 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) K2SO
4
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
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(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
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(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 H2SO
4 react with 1 mole KOH
1
moles H2SO
4 in 25.0 cm3 = 0.068 × 0.5
1
moles H2SO
4 in 1 dm3 = = 1.36 mol/dm3
1 [9]
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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
Na2CO
3 / NaHCO
3
ie sodium / sodium ions (1 mark) carbonate / carbonate ions (1 mark) incorrect formula including Na and CO
3 = 1 mark
2
(b) calcium chloride CaCl
2
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]
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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 HNO
3
= × 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
15M
1 = 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 / Na
2O
1
(iii) C = ethyl ethanoate (acetate) / CH
3COOC
2H
5 / CH
3CO
2C
2H
5
1
(iv) D = (concentrated) sulphuric acid / H
2SO
4
do not accept dilute sulphuric acid 1
E = sodium ethanoate (acetate) / CH3COONa / CH
3CO
2Na
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 NH
3 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
Na2CO
3: 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
Na2SO
4: BaCl
2 → 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
M23. (a) 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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Page 61 of 61
