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Q1. Ammonium nitrate and potassium chloride are both salts. They can be made by neutralisation reactions.
Choose substances from the box to complete the word equations for the formation of these two salts.
ammonia + ........................................ → ammonium nitrate + water
.................................. + hydrochloric acid → potassium chloride + .......................... (Total 3 marks)
ammonia hydrochloric acid nitric acid
potassium nitrate water potassium hydroxide
Q2. A student tried to make some magnesium sulphate. Excess magnesium was added to dilute sulphuric acid. During this reaction fizzing was observed due to the production of a gas.
(i) Complete and balance the chemical equation for this reaction.
..................... + H2SO
4 → ....................... + ........................
(3)
(ii) At the end of the reaction the solution remaining was filtered. Why was the solution filtered?
..................................................................................................................................... (1)
Page 1 of 39
(iii) The filtered solution was left in a warm place.
Explain why the filtered solution was left in a warm place.
.....................................................................................................................................
.....................................................................................................................................
..................................................................................................................................... (2)
(Total 6 marks)
Q3. Salts can be prepared by the reaction of acids with alkalis.
(a) (i) The reactions of acids with alkalis can be represented by the equation below. Choose a substance from the box to complete the equation.
acid + alkali → salt + .......................................................... (1)
(ii) Draw a ring around the word which best describes the reaction.
displacement neutralisation oxidation reduction (1)
carbon dioxide hydrogen oxygen water
Page 2 of 39
(b) Sodium sulphate is an important salt.
The table gives a list of some substances.
Put a tick ( ) next to the names of the acid and the alkali that would react to make sodium sulphate.
(2) (Total 4 marks)
Substances ( )
Hydrochloric acid
Nitric acid
Potassium sulphate
Sodium hydroxide
Sodium nitrate
Sulphuric acid
Q4. (a) Magnesium burns in oxygen, forming magnesium oxide.
This equation represents the reaction.
Mg (s) + O2 (g) → MgO (s)
(i) Balance the equation. (1)
(ii) Give the meaning of the state symbols (s) and (g).
(s) ..............................................
(g) .............................................. (2)
(b) Use the Formulae of Some Common Ions table on the Data Sheet to help you to answer this question.
Magnesium also reacts with chlorine to form magnesium chloride.
Give the formula of magnesium chloride .................................................................. (1)
(Total 4 marks)
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Q5. Sodium chloride solution is a useful raw material for the manufacture of other substances.
(i) What is the name of the process shown?
..................................................................................................................................... (1)
(ii) Chloride ions lose electrons at the positive electrode. What is the name of this type of reaction?
..................................................................................................................................... (1)
(iii) The solution formed at X is alkaline. What causes this solution to be alkaline?
.....................................................................................................................................
.....................................................................................................................................
..................................................................................................................................... (2)
(iv) Give a balanced ionic equation for the formation of hydrogen gas at the negative electrode.
..................................................................................................................................... (3)
(Total 7 marks)
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Q6. (a) Calcium chloride is made from limestone. Limestone contains mainly calcium carbonate and a small amount of magnesium carbonate.
(i) In stage 1 calcium carbonate reacts with acid X to form calcium chloride.
Draw a ring around the name of acid X.
(1)
hydrochloric nitric sulfuric
(ii) Stage 1 produces a concentrated solution of calcium chloride. The solution also contains magnesium chloride.
Calcium hydroxide solution is added in stage 2 to remove the magnesium chloride.
The equation for this reaction is:
Draw a ring around the correct answer to complete each sentence.
In stage 3 the solid magnesium hydroxide can be separated from the calcium chloride
(2)
MgCl2(aq) + Ca(OH)
2(aq) → Mg(OH)
2(s) + CaCl
2(aq)
dissolved
In stage 2 a precipitate is made because magnesium hydroxide is insoluble in water.
soluble
chromatography.
solution using electrolysis.
filtration.
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(iii) What method can be used to change the calcium chloride solution into solid calcium chloride? Draw a ring around your answer.
(1)
crystallisation electrolysis reduction
(b) Calcium chloride can also be made by reacting calcium with chlorine:
The diagram shows what happens to atoms of calcium and chlorine in this reaction.
The dots (●) and crosses (x) are used to represent electrons.
Only the outer electrons are shown.
Use the diagram to help you to answer this question.
Describe, as fully as you can, what happens when calcium reacts with chlorine to make calcium chloride.
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........................................................................................................................ (4)
(Total 8 marks)
calcium + chlorine → calcium chloride
Page 6 of 39
Q7. Read the information in the box and then answer the question.
Aluminium is made by the electrolysis of aluminium oxide.
Aluminium oxide is an ionic compound containing aluminium ions (Al3+) and oxide ions (O2–).
The diagram below shows the apparatus used to electrolyse aluminium oxide.
(a) In this question you will get marks on using good English, organising information clearly and using specialist terms correctly.
Use information in the box and your knowledge and understanding of this process to answer this question.
Explain, as fully as you can, how aluminium and carbon dioxide are formed in this process.
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(b) Aluminium is a metal.
Explain why aluminium conducts electricity.
........................................................................................................................
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........................................................................................................................
........................................................................................................................ (2)
(Total 8 marks)
Q8. Explain, in terms of ions and molecules, what happens when any acid reacts with any alkali.
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Q9. The electrolysis of sodium chloride solution is an important industrial process. Three useful substances are produced:
• chlorine gas is formed at the positive electrode;
• hydrogen gas is formed at the negative electrode;
• an alkali is left in the solution.
The reactions which take place at the electrodes are represented by the equations shown below:
2Cl– – 2e– → Cl2
2H+ + 2e– → H2
(a) Name the important alkali which is left in the solution.
.................................................................................................................................... (1)
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(b) State why chloride ions move towards the positive electrode.
.................................................................................................................................... (1)
(c) Why is the formation of chlorine at this electrode said to be an oxidation reaction?
.................................................................................................................................... (1)
(Total 3 marks)
Q10. Sodium chloride is a raw material.
(a) The electronic structure of a sodium atom is shown below.
Complete the diagram for the electronic structure of a chlorine atom. A chlorine atom has 17 electrons.
(1)
(b) When sodium and chlorine react to form sodium chloride they form sodium ions (Na+ ) and chloride ions (Cl– ).
How does a sodium atom change into a sodium ion?
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................ (2)
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(c) The diagram shows apparatus used in a school laboratory for the electrolysis of sodium chloride solution.
The solution contains sodium ions (Na+), chloride ions (Cl– ), hydrogen ions (H + ) and hydroxide ions (OH– ).
(i) Why do chloride ions move to the positive electrode?
............................................................................................................... (1)
(ii) Name the gas formed at the negative electrode.
............................................................................................................... (1)
(d) Chlorine and chlorine compounds are used to bleach wood pulp that is used to make paper.
The article below is from a newspaper.
(i) Why are some local people worried about the use of chlorine compounds?
...............................................................................................................
............................................................................................................... (1)
Local people have been protesting outside a paper factory. They say: ‘We want the company to stop using chlorine compounds. Chlorine compounds release poisons into the environment. The company should use safer compounds.’
The company replied: ‘Chlorine has been used safely for many years to treat drinking water. Only tiny amounts of chlorine are released, which cause no harm. Using other compounds will be more expensive and may put us out of business.’
(ii) Why might other local people want the company to continue to use chlorine compounds?
...............................................................................................................
............................................................................................................... (1)
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(iii) It is decided to have an inquiry. Why should this be done by independent scientists?
...............................................................................................................
............................................................................................................... (1)
(Total 8 marks)
Q11. Waste water from some industrial processes contains harmful metal ions, such as chromium ions. These ions must be removed from the water before the water is returned to a river.
The equation shows a method of removing chromium ions from water.
CrCl3(aq) + 3NaOH(aq) → Cr(OH)
3(s) + 3NaCl(aq)
(a) This type of reaction is called a precipitation reaction.
Describe what happens in a precipitation reaction
........................................................................................................................
........................................................................................................................ (1)
(b) Complete the name of the substance with the formula NaOH.
Sodium ........................................ (1)
(c) Draw a ring around the method that could be used to separate the Cr(OH)3(s) from the
water.
electrolysis filtration neutralisation oxidation (1)
(d) It is important to remove chromium ions from water before it is returned to a river.
Suggest why.
........................................................................................................................
........................................................................................................................ (1)
(Total 4 marks)
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Q12. The electrolysis of sodium chloride solution is an industrial process.
(a) Why do chloride ions move to the positive electrode?
........................................................................................................................ (1)
(b) Sodium chloride solution contains two types of positive ions, sodium ions (Na+) and
hydrogen ions (H+).
Tick ( ) the reason why hydrogen is produced at the negative electrode and not sodium.
(1)
Reason Tick ( )
Hydrogen is a gas.
Hydrogen is less reactive than sodium.
Hydrogen is a non-metal.
Hydrogen ions travel faster than sodium ions.
(c) Solution X is alkaline.
Which ion makes solution X alkaline?
........................................................................................................................ (1)
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(d) Electrolysis of sodium chloride solution produces hydrogen and chlorine. The hydrogen and chlorine can be used to make hydrogen chloride.
(i) The diagrams show how the outer electrons are arranged in atoms of hydrogen and chlorine.
Complete the diagram to show how the electrons are arranged in a molecule of hydrogen chloride (HCl).
(1)
(ii) Name the type of bond between the hydrogen and the chlorine atoms in a molecule of hydrogen chloride.
................................................................................ (1)
(iii) Some hydrogen chloride was bubbled into water. This made a solution with a pH of 1.
Which ion gave the solution a pH of 1?
................................................................................ (1)
(Total 6 marks)
Q13. (a) Copper sulfate crystals can be made from copper oxide and dilute sulfuric acid.
In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.
Give a method for making copper sulfate crystals from copper oxide and dilute sulfuric acid.
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You should include:
• the names of the pieces of apparatus used
• the purpose of each step
• appropriate safety precautions.
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(b) If crystals of hydrated copper(II) sulfate are dried by heating them strongly, they decompose to give a white solid.
The equation for this decomposition is:
CuSO4. 5H
2O CuSO
4 + 5H
2O
(i) Give the name of the white solid formed.
............................................................................................................... (1)
(ii) Dilute sulfuric acid was added to the white solid. What colour would the white solid turn? Explain your answer.
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(Total 9 marks)
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Q14. The diagram represents an electrolysis cell for extracting aluminium. The current will only flow when the electrolyte is molten.
(a) The electrolyte is aluminium oxide mixed with another substance.
(i) What is the name of the other substance in the electrolyte?
Draw a ring around the correct answer.
(1)
cryolite rock salt limestone
(ii) Draw a ring around the correct answer to complete the sentence.
(1)
condense the aluminium oxide.
This other substance is added to lower the melting point of the aluminium oxide.
raise the boiling point of the aluminium oxide.
(b) (i) Oxide ions (O2−) move to the positive electrode.
Explain why.
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........................................................................................................................
........................................................................................................................ (2)
(ii) Oxygen is formed at the positive electrode. The oxygen then forms carbon dioxide.
The equation for the reaction is shown below.
C + O2
→ CO2
Complete the sentence.
The name of the element which reacts with oxygen is ................................. (1)
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(iii) The positive electrode gets smaller.
Suggest why.
........................................................................................................................
........................................................................................................................ (1)
(c) Aluminium is used in an alloy with magnesium to make drinks cans.
The diagrams show the arrangement of atoms in pure aluminium and in the alloy.
The alloy is harder than pure aluminium.
Explain why. Use the diagrams to help you.
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........................................................................................................................ (2)
(Total 8 marks)
Q15. Diagram 1 shows the apparatus used to electrolyse magnesium sulfate solution.
Diagram 1
Gases were given off at both electrodes.
Page 16 of 39
(a) The gas collected at the anode was oxygen.
Draw one line from the test for oxygen to the correct result.
(1)
(b) (i) The gas collected at the cathode was hydrogen.
Describe how to test the gas to show that it is hydrogen.
Test ......................................................................................................
...............................................................................................................
Result ....................................................................................................
............................................................................................................... (2)
(ii) Why is hydrogen, and not magnesium, produced at the cathode?
...............................................................................................................
............................................................................................................... (1)
(c) A student wanted to use electrolysis to silver plate a metal spoon.
(i) Give one reason why metal spoons are sometimes silver plated.
...............................................................................................................
............................................................................................................... (1)
Page 17 of 39
(ii) Diagram 2 shows the apparatus the student used. The student did not set the apparatus up correctly.
Diagram 2
d.c. power supply
The student found that the metal spoon eroded and a thin layer of copper formed on the pure silver electrode.
Suggest two changes that the student must make to his apparatus to be able to silver plate the metal spoon. Give a reason for each change.
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(iii) Why is it difficult to electroplate plastic spoons?
...............................................................................................................
............................................................................................................... (1)
(Total 10 marks)
Page 18 of 39
Q16. The salt sodium hydrogen phosphate (Na2HPO
4) is used as a softening agent in
processed cheese.
It can be made by reacting phosphoric acid (H3PO
4) with an alkali.
(a) Complete the name of an alkali that could react with phosphoric acid to make sodium hydrogen phosphate.
....................................... hydroxide (1)
(b) What is the name given to a reaction in which an acid reacts with an alkali to make a salt?
..................................................................................................................................... (1)
(c) How would the pH change when alkali is added to the phosphoric acid solution?
.....................................................................................................................................
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(d) What ions are present when any acid is dissolved in water?
..................................................................................................................................... (1)
(e) What ions are present when any alkali is dissolved in water?
..................................................................................................................................... (1)
(f) Write a chemical equation for the reaction which takes place between the ions you have named in (e) and (f).
..................................................................................................................................... (1)
(Total 6 marks)
Page 19 of 39
Q17. Electroplating is used to coat a cheap metal with a thin layer of an expensive metal.
In the diagram a teaspoon made of nickel is being coated with silver.
Silver nitrate (AgNO3) contains silver ions (Ag+) and nitrate ions (NO
3
−).
(a) Solid silver nitrate, AgNO3(s), does not conduct electricity.
Choose the correct answer in the box to complete the sentence.
Solid silver nitrate does not conduct electricity because the ions ................
........................................................................................................................ (1)
are too big cannot move are too small
(b) Draw a ring around the correct answer to complete each sentence.
(1)
no charge.
(i) Silver ions move to the negative electrode because they have a negative charge.
a positive charge.
(1) (Total 3 marks)
atoms.
(ii) When silver ions reach the negative electrode they turn into silver compounds.
molecules.
Page 20 of 39
Q18. The electrolysis of sodium chloride solution is an industrial process.
The diagram shows the apparatus used in a school experiment.
(a) One of the products of the electrolysis of sodium chloride solution is hydrogen.
(i) Why do hydrogen ions move to the negative electrode?
...............................................................................................................
............................................................................................................... (1)
(ii) How does a hydrogen ion change into a hydrogen atom?
...............................................................................................................
............................................................................................................... (1)
(b) Hydrogen is used to make ammonia (NH3).
Complete the diagram to show the bonding in ammonia.
Use dots (●) and crosses (x) to show electrons.
Show only outer shell electrons.
(2)
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(c) The table shows the ions in sodium chloride solution.
In industry, some of the waste from the electrolysis of sodium chloride solution is alkaline and has to be neutralised.
(i) Which ion makes the waste alkaline?
............................................................................................................... (1)
Positive ions Negative ions
hydrogen chloride
sodium hydroxide
(ii) This waste must be neutralised.
Write the ionic equation for the neutralisation reaction.
............................................................................................................... (1)
(d) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.
The electrolysis of sodium chloride solution also produces chlorine and sodium hydroxide.
In industry, the electrolysis of sodium chloride solution can be done in several types of electrolysis cell.
Some information about two different types of electrolysis cell is given below.
Mercury cell Membrane cell
Cost of construction Expensive Relatively cheap
Additional substances used
Mercury, which is recycled. Mercury is toxic so any traces of mercury must be removed from the waste
Membrane, which is made of a polymer. The membrane must be replaced every 3 years.
Amount of electricity used for each tonne of chlorine produced in kWh
3400 2950
Quality of chlorine produced Pure
Needs to be liquefied and distilled to make it pure.
Quality of sodium hydroxide solution produced
50% concentration. Steam is used to concentrate the sodium hydroxide solution produced.
30% concentration. Steam is used to concentrate the sodium hydroxide solution produced.
Page 22 of 39
Use the information and your knowledge and understanding to compare the environmental and economic advantages and disadvantages of these two types of electrolysis cell.
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(Total 12 marks)
Q19. Copper sulfate (CuSO4) is a salt that has many uses.
An aqueous solution of copper sulfate can be made by reacting copper oxide (CuO) with an acid.
(a) (i) Name this acid. ............................................................................................... (1)
(ii) Write a balanced symbol equation, including state symbols, for this reaction.
......................................................................................................................... (2)
Page 23 of 39
(b) Copper oxide reacts much faster with acid at 40 °C than at 20 °C.
Explain why in terms of particles.
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(Total 5 marks)
Page 24 of 39
M1. nitric acid 1
potassium hydroxide 1
water 1
[3]
M2. (i) Mg + (H2SO
4) →
1
MgSO4 + 1
H2
deduct 1 mark if not balanced only if all three correct accept alternative metal of similar reactivity for example Zn or Fe candidate would not then be awarded first mark for Mg then error carried forward deduct 1 mark if not balanced only if all three correct
1
(ii) to remove the (excess) magnesium accept separate accept insoluble substances or solids or residue do not accept unreactive substances or impurities or remove magnesium from sulphuric acid
1
(iii) to evaporate (some of the water or solution) 1
to form crystals or crystallise
accept to form a saturated solution or concentrated solution do not accept to leave MgSO
4
1 [6]
M3. (a) (i) water
accept H2O
accept correct ringed answer in box 1
(ii) neutralisation accept underlining or any indication, eg tick
1
Page 25 of 39
(b) sodium hydroxide 1
sulphuric acid apply list principletotal
1 [4]
M4. (a) (i) 2 Mg + O2 → 2 MgO
both 2s needed
allow O2 or any correct multiple
1
(ii) solid 1
gas 1
(b) MgCl2 / C1
2Mg
do not accept MG mg mG CL cl cL ignore charges
1 [4]
M5. (i) electrolysis 1
(ii) oxidation 1
(iii) hydroxide ions or OH–
accept sodium hydroxide or hydroxide or OH for one mark only 2
(iv) H+ + e–
1
H2
ignore any state symbols 1
2H+ + 2e– → H2
accept H+ + e-→ H for one mark only
1 [7]
Page 26 of 39
M6. (a) (i) hydrochloric 1
(ii) insoluble 1
filtration 1
(iii) crystallisation 1
(b) any four from:
any reference to incorrect bonding = max 3
• calcium atom reacts with 2 chlorine atoms
• calcium atoms lose electrons accept calcium ion is formed
• lose two electrons
accept calcium has a 2+ charge / calcium ion has a 2+ charge
allow Ca2+
• chlorine atoms gain electrons
accept chloride ion formed
• gain one electron
accept chlorine / chloride has a negative charge / is a negative ion/ is a negative particle
allow Cl–
if no other marks awarded allow ionic bonding or complete outer shell for 1 mark
4 [8]
M7. (a) 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 electrolysis of aluminium oxide. Level 1 (1–2 marks)
There is some description of the electrolysis of aluminium oxide. Level 2 (3–4 marks)
There is a clear, balanced and detailed description of the electrolysis of aluminium oxide.
Level 3 (5–6 marks)
Page 27 of 39
examples of the chemistry points made in the response
• aluminium oxide is melted / made liquid
• aluminium ions are attracted to the negative electrode
• at the negative electrode aluminium is formed or aluminium ions gain electrons
• oxide ions are attracted to the positive electrode
• oxygen is formed at the positive electrode or oxide ions lose electrons
• the oxygen reacts with carbon to make carbon dioxide or carbon dioxide formed at positive electrode.
(b) there are delocalised electrons / free electrons / electrons which move within the aluminium / metallic structure
1
therefore these electrons are able to carry the current / charge 1
if the candidates use the terms covalent / ionic / molecules / intermolecular incorrectly in the answer this will limit the mark to a maximum of 1.
[8]
M8. hydrogen ions (from acid) or protons / H+
1
react with hydroxide ions (from alkali) / OH1
to produce water
H + OH H2O gains all 3 marks
ignore state symbols molecules of hydrogen ions and molecules of hydroxide ions produce water = 2 marks if they fail to get any of the above marks they can get 1 mark for neutralisation / product neutral
1 [3]
M9. (a) sodium hydroxide / caustic soda / NAOH
for 1 mark 1
Page 28 of 39
(b) negative ions move to the positive electrode etc. /because it is negative /opposite charges attract
for 1 mark 1
(c) loss of electrons for 1 mark
1 [3]
M10. (a)
accept dots / crosses / e must be drawn on diagram electrons do not need to be paired ignore brackets or + or -charges ignore 2,8,7
1
(b) (one) electron recognition that electrons are involved
1
lost / given away / transferred from sodium / transferred to chlorine owtte must be linked to electrons accept loses electron(s) for 2 marks NB loses 2 or more electrons gains 1 mark reference to sharing / covalent max 1 mark ignore charges on ions formed
1
(c) (i) any one from:
• ions / atoms / they are / it is negatively charged / anions accept they are negative
• opposite (charges) attract accept they are attracted or it is oppositely charged ignore opposite forces attract
1
Page 29 of 39
(ii) hydrogen accept H
2
ignore H or H+
1
(d) (i) poisons released into environment (owtte) accept any sensible idea of harm / harmful / poisons / poisonous / pollution / damaging do not accept answers such as global warming / ozone layer etc. ignore safety unless qualified
1
(ii) any one sensible idea eg
• loss of work / unemployment eg shops / house prices etc.
or company goes out of business
• any adverse effect on local economy (owtte)
• any adverse effect on paper production / cost of paper / cost of water (treatment) allow less expensive to use chlorine or converse
• chlorine (compounds) have been used (for many years) without causing harm owtte
• only a tiny amount of chlorine is released so it would not cause harm ignore uses of chlorine to treat drinking water unless qualified
1
(iii) ideas related to bias accept more reliable or valid or fair ignore more accurate / fair test
1 [8]
Page 30 of 39
M11. (a) a solid / insoluble salt is formed
accept salt / substance that does not dissolve forms 1
(b) hydroxide 1
(c) filtration 1
(d) risk is that chromium ions are toxic or harmful 1
[4]
M12. (a) any one from:
• they are negative / anions
allow Cl–
ignore atoms / chlorine do not accept chloride ions are negative electrodes
• they are attracted
• they are oppositely charged 1
(b) hydrogen is less reactive than sodium 1
(c) hydroxide (ions) / OH–
ignore OH do not accept NaOH / sodium hydroxide
1
(d) (i)
allow any combination of dots or crosses ignore chemical symbols
1
(ii) covalent allow close spelling errors apply list principle
1
Page 31 of 39
(iii) hydrogen (ion) / H+
ignore (aq) / H do not accept hydrochloric acid / HCl apply list principle
1 [6]
M13. (a) Marks awarded for this answer will be determined by the quality of communication as well as the standard of the scientific response.
0 marks No relevant content
Level 1 (1–2 marks) There is a basic method, which includes some of the apparatus,and there is some attempt at explaining some of the steps. The method does not necessarily allow the procedure to be completed successfully by another person.There may be an attempt at identifying safety precautions but these may be inappropriate or incomplete.
Level 2 (3–4 marks) There is a clear description of the method, which includes most of the apparatus needed, and an explanation of the various steps in the procedure. The method could be followed by another person. There is some attempt at identifying some, but not necessarily all, of the safety precautions needed.
Level 3 (5–6 marks) There is a clear, balanced and detailed description of the method, which correctly names the apparatus needed and explains the purpose of each step.This method could easily be followed by another person. There is a comprehensive list of appropriate safety precautions.
Page 32 of 39
examples of chemistry points made in the response
extra information
• heat the sulfuric acid in a beaker and add the copper oxide with stirring the underlined words are needed to gain each point
• because heating and stirring speed up the reaction
• until the copper oxide is in excess
• which means that the reaction has gone to completion
• filter the mixture or pour the mixture through a funnel and filter paper or leave the mixture to stand and decant / pour off the excess liquid
• to remove the excess / unreacted copper oxide
• put the solution in an evaporating basin
• heat it gently so that (some of) the water evaporates
• when a saturated solution is formed or when crystals start to form, stop heating
• leave the solution to cool so that crystallisation can occur.
examples of the safety points made in the response
• wear safety goggles – to protect eyes because sulfuric acid is corrosive / an irritant / harmful
• care when heating – to protect against burns
• wash hands after the preparation – copper sulfate is harmful / a sensitiser
• care when handling glass apparatus – to protect against cuts
• do not add copper oxide to boiling acid as it may boil over 6
(b) (i) anhydrous copper sulfate do not accept ‘dehydrated’
1
(ii) it (turns) blue 1
because (dilute sulfuric acid) contains water or because (dilute sulfuric acid) rehydrates the crystals or because hydrated copper sulfate is formed
owtte ignore references to forming a solution / dissolving
1 [9]
Page 33 of 39
M14. (a) (i) cryolite 1
(ii) lower the melting point of the aluminium oxide 1
(b) (i) opposite charges or oxide ions are negative 1
attract 1
(ii) carbon 1
(iii) reacts with oxygen or forms carbon dioxide
accept burns 1
(c) Structure mark:
either Al (atoms) in layers / rows
accept Al (atoms) all the same size allow Al (atoms) in lines
or alloy (atoms) not in layers / rows
accept different sizes of atoms in alloy allow alloy (atoms) not in lines
1
Sliding mark:
either so (Al layers) can slide
or so (alloy) layers cannot slide 1
[8]
M15. (a)
more than one line from test negates the mark
1
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(b) (i) place a lighted splint at the mouth of the tube 1
there is a squeaky pop dependent on correct test
1
(ii) hydrogen is less reactive than magnesium accept converse accept magnesium is too reactive
1
(c) (i) any one from:
• to improve appearance or make it look nice • to prevent corrosion • to make it more durable • cheaper than solid silver
1
(ii) solution must be silver nitrate or contain silver ions 1
otherwise copper will be deposited or silver will not be deposited 1
spoon must be the negative electrode / cathode 1
because silver ions have a positive charge or go to negative electrode or are discharged at the negative electrode.
1
(iii) because (plastic is an) insulator or does not conduct electricity
accept does not contain mobile electrons 1
[10]
M16. (a) sodium 1
(b) neutralisation 1
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(c) increase/inc. number 1
(d) H+
1
(e) OH–
1
(f) H+ + OH– → H2O
1 [6]
M17. (a) cannot move 1
(b) (i) a positive charge 1
(ii) atoms 1
[3]
M18. (a) (i) because they are positively charged
accept they are positive / H+
accept oppositely charged or opposites attract
ignore they are attracted 1
(ii) gains one / an electron
accept H+ + e– → H or multiples
allow gains electrons 1
(b) 3 bonding pairs 1
1 lone pair accept 2 non-bonding electrons on outer shell of nitrogen
1
(c) (i) hydroxide / OH–
do not accept sodium hydroxide 1
(ii) H+ + OH– → H2O
ignore state symbols ignore word equation
1
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(d) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the information in the Reference material.
0 marks No relevant content.
Level 1 (1-2 marks) There are basic descriptions of advantages or disadvantages of the electrolysis cells.
Level 2 (3-4 marks) There are clear descriptions of environmental or economic advantages or disadvantages of the electrolysis cells. Comparisons may be implied.
Level 3 (5-6 marks) There are detailed descriptions of environmental and economic advantages and disadvantages, comparing the electrolysis cells.
Examples of chemistry points made in the response:
Accept converse where appropriate.
• mercury cell is more expensive to construct
• mercury is recycled but membranes must be replaced
• mercury is toxic but membrane / polymer is not
• removing traces of mercury from waste is expensive
• mercury cell uses more electricity
• mercury cell produces chlorine that is purer
• mercury cell produces higher concentration / better quality of sodium hydroxide (solution)
6 [12]
M19. (a) (i) sulfuric
accept H2SO
4
accept sulphuric allow phonetic spellings
1
(ii) CuO + H2SO
4 → CuSO
4 + H
2O
1 mark for reactants 1 mark for products ignore state symbols max 1 mark for incorrect balancing
2
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(b) any two from:
• particles gain energy or particles have more energy
allow have more activation energy
• particles move faster allow they collide faster / quicker ignore move / vibrate more
• collide more often allow more collisions
• collide more energetically
• more of the collisions are successful or more particles have the activation energy
NB more successful collisions alone = 1 mark if particles are identified as electrons = max 1 mark
2 [5]
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