A Level Official Exam Material
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Unit 2: Energetics, Group Chemistry, Halogenoalkanes and Alcohols
Topic 8: Redox Chemistry and Groups 1, 2 and 7
For both AS and A Level students
Q1. In which reaction is calcium oxidised? (1)
A Ca + 2HCl → CaCl2 + H2
B CaO + 2K → Ca + K2O
C CaO + H2O → Ca(OH)2
D CaCO3 → CaO + CO2
(Total for question = 1 mark)
Q2. Consider the following ionic half-equations Al → Al3+ + 3e– 2H+ + 2e– → H2
When these ionic half-equations are combined, the full ionic equation is (1)
A Al + 2H+ → Al3+ + H2
B Al + 2H+ + 2e– → Al3+ + H2 + 3e–
C Al + 6H+ → Al3+ + 3H2
D 2Al + 6H+ → 2Al3+ + 3H2
(Total for question = 1 mark)
Q3. The oxidation number of chlorine in HClO3 is
A −1
B +3
C +5
D +7
(Total for question = 1 mark)
Q4. The oxidation number of sulfur in potassium aluminium sulfate (potash alum), KAl(SO4)2.12H2O, is
A –2
B +2
C +6
D +8
(Total for question = 1 mark)
Q5. This is a question about catalysis. A spectacular demonstration of catalytic oxidation is the addition of chromium(III) oxide to ammonia gas in the presence of oxygen.
This produces flashes, sometimes described as 'fireflies'.
Some concentrated ammonia solution is allowed to vaporise in a very large flask.
Heated chromium(III) oxide catalyst is added. The equation below shows one possible reaction.
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
(a) The nitrogen atoms in ammonia are oxidized.
Give the oxidation numbers of the nitrogen atoms in ammonia and nitrogen monoxide. (2) NH3...........................................................
NO...........................................................
(b) The chromium(III) oxide catalyst can be produced from a remarkable demonstration commonly called the 'dichromate volcano'.
One experimental apparatus that could be used is shown below.
(i) The substance used is ammonium dichromate(VI).
Give the formula of ammonium dichromate(VI). (1)
(Total for question = 3 marks)
Q6. (a) When concentrated sulfuric acid is added to solid potassium bromide, a redox reaction occurs.
A mixture of products is formed, including sulfur dioxide as the only reduction product.
(i) Give the oxidation number of sulfur in (2)
sulfuric acid.....................................................................................................
sulfur dioxide...................................................................................................
(ii) Complete the ionic equation for this redox reaction.
State symbols are not required.
(Total for question = 4 marks)
Q7. This question is about some aspects of the chemistry of iodine and its compounds.
In industry, the main source of iodine is sodium iodate(V), NaIO3, which occurs in deposits found in Chile.
In the human body, iodide ions, I– , are needed for the thyroid gland to function properly. In many countries, potassium iodide, KI, is added to table salt as a source of iodide ions.
(a) In the production of iodine, the final stage involves the reaction between sodium iodate(V) and sodium iodide in acidic solution.
The ionic half-equations for the redox processes are as follows.
IO + 6H+ + 5e– → ½I2 + 3H2O I – → ½I2 + e–
(i) Use these half-equations to deduce the full ionic equation for the production of iodine by this process.
State symbols are not required. (2)
(ii) Identify, by its formula, the oxidizing agent in the reaction in
(a)(i). Justify your answer in terms of electron transfer. (2) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(b) On addition of concentrated sulfuric acid to crystals of potassium iodide, solid sulfur and a black solid are observed amongst the products formed.
(i) Identify, by name or formula, the black solid. (1) .............................................................................................................................................
(ii) Construct the ionic half–equation for the formation of sulfur from concentrated sulfuric acid.
State symbols are not required. (2)
(iii) When iodide ions react with concentrated sulfuric acid, another product, X, can also be detected. X is a toxic gas with a smell of rotten eggs.
Identify X, by name or formula, and give the oxidation numbers of sulfur when X is formed from concentrated sulfuric acid. (3) Identity of gas X:
Oxidation number of S in sulfuric acid is ...........................................................
Oxidation number of S in X is ...........................................................
(ii) Suggest a reason, other than cost, why some countries do not add potassium iodide to table salt. (1) ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 10 marks)
Q8. A colourless solid, Q, was warmed with sodium hydroxide solution.
A gas was evolved which turned damp red litmus paper blue. What is solid Q? (1)
A NaNO3
B NH4Cl
C NaCl
D Ca(NO3)2
(Total for question = 1 mark)
Q9. Answer the questions with a cross in the boxes you think are correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
A white solid, X, gives a red colour in the flame test and a cream precipitate forms when acidified silver nitrate solution is added to a solution of X.
(a) What is the white solid, X? (1)
A lithium chloride
B calcium chloride
C strontium bromide
D barium bromide
(b) What causes the flame colour to be red? (1)
A electrons absorb blue and green light as they are promoted
B electrons emit red light as they are promoted
C blue and green light is absorbed as electrons return to lower energy levels
D red light is emitted as electrons return to lower energy levels
Use this space for any rough working. Anything you write in this space will gain no credit.
(Total for question = 2 marks)
Q3. Which statement is correct? (1)
A barium carbonate is less stable to heat than magnesium carbonate
B barium hydroxide is less soluble in water than magnesium hydroxide
C barium sulfate is less soluble in water than magnesium sulfate
D barium metal is less reactive with water than magnesium metal
(Total for question = 1 mark)
Q10. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which of these compounds does not produce a colour in a flame test, and produces an alkaline gas when warmed with sodium hydroxide solution?
A Ca(OH)2
B Mg(OH)2
C NH4Cl
D BeCl2
(Total for question = 1 mark)
Q11. Which statement is not explained by hydrogen bonding? (1)
A all Group 1 hydroxides are soluble in water
B many simple alcohols are soluble in water
C the density of ice is less than the density of liquid water at 0 °C
D the melting temperature of water is abnormally high
(Total for question = 1 mark)
Q12. Compound X gives a red flame test colour and a white precipitate on addition of dilute hydrochloric acid followed by barium chloride solution.
Which compound is X? (1)
A calcium chloride
B lithium sulfate
C potassium sulfate
D strontium chloride
(Total for question = 1 mark)
Q13. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross . Compound Q gives off nitrogen dioxide when heated, and produces a red colour in a flame test.
(a) Which of these compounds could be Q? (1)
A barium nitrate
B lithium nitrate
C magnesium nitrate
D rubidium nitrate
(b) Which colour and test results are correct for nitrogen dioxide gas? (1)
Q14. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which is the ionic equation for the reaction of solid barium carbonate with dilute hydrochloric acid?
Q15. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Several factors may affect ionisation energies:
I) the number of protons increases
II) the outer electron is further from the nucleus
III) the amount of shielding increases
IV) the number of unpaired outer electrons increases
Which factors explain the decrease in ionisation energy as Group 1 is descended?
A I and II
B II and III
C III and IV
D I, II, III and IV
(Total for question = 1 mark)
Q16. Which process explains the flame colour produced by the compounds of Group 1 elements? (1)
A absorption of visible light energy as electrons are promoted to higher energy levels
B absorption of visible light energy as electrons are removed from gaseous atoms
C emission of visible light energy as electrons return to lower energy levels
D emission of visible light energy as electrons are added to gaseous ions
(Total for question = 1 mark)
Q17. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which of these sulfates is the least soluble in water?
A CaSO4
B BaSO4
C K2SO4
D Rb2SO4
(Total for question = 1 mark)
Q18. For each question, select one answer from A to D and put a cross in the box .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Four tests used to identify ions are shown: 1 flame test 2 addition of acidified barium nitrate solution 3 addition of acidified silver nitrate solution 4 addition of sodium hydroxide solution, then testing any gas with indicator paper Which tests could be used to positively identify the ions in ammonium chloride?
A 1 and 2
B 1 and 3
C 2 and 4
D 3 and 4
(Total for question = 1 mark)
Q19. A student made the following statements about trends going down Group 2.
Which statement is correct? (1)
A the thermal stability of the nitrates decreases
B the thermal stability of the carbonates decreases
C the solubility of hydroxides increases
D the solubility of sulfates increases
(Total for question = 1 mark)
Q20. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
(a) A pellet of sodium hydroxide has a mass of 0.700 g.
Some pellets were dissolved to make 350 cm3 of 0.25 mol dm–3 solution. [Mr value: NaOH = 40]
How many pellets were dissolved? (1)
A 4
B 5
C 8
D 125
(b) 25.0 cm3 of the sodium hydroxide solution prepared in
(a) was placed in a conical flask and titrated with sulfuric acid.
2NaOH + H2SO4 → Na2SO4 + 2H2O
Calculate the number of moles of sulfuric acid that reacted. (1)
A 0.0031
B 0.0063
C 0.013
D 0.044
(c) Phenolphthalein indicator was used for the titration in (b).
What was the colour change at the endpoint? (1)
A colourless → pink
B pink → colourless
C orange → yellow
D yellow → orange
Use this space for any rough working.
Anything you write in this space will gain no credit.
(Total for question = 3 marks)
Q21. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Barium chloride solution, BaCl2(aq), reacts with gallium sulfate solution, Ga2(SO4)3(aq) to form a precipitate of barium sulfate, BaSO4(s).
What is the minimum volume of 0.100 mol dm−3 barium chloride needed to precipitate all the sulfate ions in 200 cm3 of 0.05 mol dm−3 gallium sulfate?
A 100 cm3
B 200 cm3
C 300 cm3
D 400 cm3
(Total for question = 1 mark)
Q22. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
What volume, in dm3 , of hydrogen gas will be produced when 3.00 g of lithium is reacted with water at room temperature and pressure (r.t.p.)? 2Li + 2H2O → 2LiOH + H2
[Molar volume of gas at r.t.p. = 24.0 dm3 mol–1 ]
A 0.217
B 0.435
C 5.22
D 10.4
(Total for question = 1 mark)
Q23. For each question, select one answer from A to D and put a cross in the box .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
A titre of 13.25 cm3 was obtained using a 50 cm3 burette.
What is the percentage uncertainty in the titre?
[Each reading of the burette has an uncertainty of ± 0.05 cm3 ]
A ± 0.38 %
B ± 0.75 %
C ± 1.5 %
D ± 7.5 %
(Total for question = 1 mark)
Q24. Answer the questions with a cross in the boxes you think are correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
A titration is carried out by adding dilute sulfuric acid from a burette to aqueous sodium hydroxide in a conical flask.
The indicator is methyl orange.
(a) What is the colour change of the indicator at the end-point of this titration? (1)
A red to orange
B red to yellow
C yellow to orange
D yellow to red
(b) A student carried out the first titration and did not notice that there was an air bubble between the tap and the tip of the burette.
During the titration, the air bubble filled with acid.
The student then carried out two accurate titrations in which there was no air bubble in the burette.
There were no other errors in these titrations.
Which of these could be the three titres for this student? (1)
(c) 25.0 cm3 of 0.100 mol dm−3 aqueous sodium hydroxide required a mean titre of 18.70 cm3 of sulfuric acid.
2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l) What is the concentration, in mol dm−3 , of the sulfuric acid? (1)
A 0.0374
B 0.0668
C 0.134
D 0.267
(Total for question = 3 marks)
Q24. Magnesium oxalate, MgC2O4 , decomposes on heating to form magnesium carbonate and carbon monoxide.
MgC2O4(s) → MgCO3(s) + CO(g)
(a) A 6.0 g sample of magnesium oxalate was heated for three minutes but the decomposition was only 70 % complete.
Calculate the total mass of solid that remains. (4)
(b) In practice, magnesium carbonate also decomposes on stronger heating.
Describe and explain the trend in the thermal decomposition of Group 2 carbonates. (3) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(c) Suggest why a pure sample of magnesium carbonate will not be produced from the decomposition of magnesium oxalate even if the sample is heated for longer. (1) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 8 marks)
Q25. This question is about calcium carbonate, CaCO3.
(a) Calcium carbonate decomposes on heating.
CaCO3(s) → CaO(s) + CO2(g)
Explain why calcium carbonate decomposes at a higher temperature than magnesium carbonate, in terms of the charge and size of the cations. (3)
............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(b) Calcium carbonate reacts with dilute hydrochloric acid.
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
A student determines the initial rate of this reaction by collecting the carbon dioxide in a gas syringe and measuring the volume at regular time intervals.
(i) The gas syringe can measure a maximum of 100 cm3 of gas.
Calculate the maximum volume of 0.500 mol dm−3 hydrochloric acid that can be added to excess calcium carbonate at room temperature and pressure (r.t.p.) without exceeding the measurable volume of the gas syringe.
[Molar volume of gas at r.t.p. = 24 000 cm3 mol−1 ] (3)
(Total for question = 6 marks)
Q26. This question is about compounds containing Group 2 elements.
(a) Hydrated magnesium nitrate has the formula Mg(NO3)2.xH2O.
A student devised an experiment to determine the value of x by leaving 5.12 g of hydrated magnesium nitrate for several hours in a warm oven.
After this time, the solid remaining had a mass of 2.97 g.
(i) State why the student used a warm oven to remove the water from the hydrated salt, rather than direct heating with a Bunsen burner. (1)
............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(ii) Use the data obtained by the student to calculate the value of x.
You must show your working. (4)
(iii) Explain the trend in thermal stability of Group 2 carbonates. (4) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(Total for question = 9 marks)
Q27. This question is about ethanoic acid and some related salts.
(a) A test to confirm the presence of an aqueous acid is adding a small amount of solid sodium carbonate to the solution. Describe two observations you would see in this test. (2) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................
(Total for question = 2 marks)
Q28. This question is about Group 1 metals.
(a) When potassium is placed into a beaker of cold water, potassium hydroxide and hydrogen are formed.
(i) Write the equation for this reaction.
Include state symbols. (2)
(ii) This is a redox reaction. State which element is oxidised and which is reduced.
Justify your answer by giving the initial and final oxidation numbers of any element that changes oxidation state. (2) ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. ............................................................................................................................................. .............................................................................................................................................
(iii) The reaction of potassium with water is very vigorous and a flame is seen. State the colour of the flame. (1) .............................................................................................................................................
Q29. For each question, select one answer from A to D and put a cross in the box .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which sequence shows the molecules in order of increasing boiling temperature?
A H2O < Br2 < Cl2 < CH4
B Br2 < CH4 < Cl2 < H2O
C Cl2 < CH4 < H2O < Br2
D CH4 < Cl2 < Br2 < H2O
(Total for question = 1 mark)
Q30. Which statement is not correct? (1)
A chlorine is more electronegative than bromine
B chlorine is more reactive than bromine
C chloride ions are stronger reducing agents than bromide ions
D chloride ions are stronger reducing agents than fluoride ions
(Total for question = 1 mark)
Q31. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Aqueous chlorine is added to an aqueous solution of potassium iodide.
A non-polar organic solvent is then added and the mixture is shaken.
The layers are allowed to separate.
What colour is seen in the organic layer?
A brown
B green
C orange
D violet
Use this space for any rough working. Anything you write in this space will gain no credit.
(Total for question = 1 mark)
Q32. What are the gaseous products formed, other than water vapour, when concentrated sulfuric acid is added to potassium bromide? (1)
A bromine and sulfur dioxide only
B bromine, hydrogen bromide and hydrogen sulfide only
C bromine, hydrogen bromide and sulfur dioxide only
D bromine, hydrogen bromide, sulfur dioxide and hydrogen sulfide only
(Total for question = 1 mark)
Q33. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which statement about the Group 7 elements chlorine, bromine and iodine is not correct?
A boiling temperature increases down the group
B reactivity increases down the group
C first ionisation energy decreases down the group
D electronegativity decreases down the group
(Total for question = 1 mark)
Q34. A white solid X produces a red colour in a flame test.
When aqueous silver nitrate and nitric acid are added to a solution of X, a cream precipitate is formed which dissolves in concentrated aqueous ammonia.
What is the formula of X?
A SrBr2
B NaBr
C LiCl
D BaI2
(Total for question = 1 mark)
Q8. When chlorine is reacted with hot concentrated potassium hydroxide, the chlorine undergoes disproportionation. What are the oxidation states of chlorine in the products? (1)
A –1 and +3
B –1 and +5
C +1 and –1
D +1 and +5
(Total for question = 1 mark)
Q35. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross . Potassium chloride reacts with concentrated sulfuric acid, producing misty fumes.
It can be deduced that
A sulfuric acid is acting as an oxidising agent
B chloride ions are acting as an oxidising agent
C hydrogen chloride is formed in the reaction
D chlorine is formed in the reaction
(Total for question = 1 mark)
Q36. Which of these products are formed when chlorine is passed through cold, dilute aqueous sodium hydroxide? (1)
A NaCl and NaClO
B NaClO and NaClO3
C NaCl and NaClO3
D NaClO and NaClO4
(Total for question = 1 mark)
Q37. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Solid potassium bromide reacts with concentrated sulfuric acid.
Which of these substances does not form?
A bromine
B hydrogen bromide
C hydrogen sulfide
D sulfur dioxide
(Total for question = 1 mark)
Q38. Potassium iodide reacts with concentrated sulfuric acid.
Which of the following is not a product? (1)
A H2S
B I2
C S
D SO3
(Total for question = 1 mark)
Q39. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
When iodine is dissolved in a non-polar organic solvent, the solution formed is
A purple B orange
C colourless
D brown
(Total for question = 1 mark)
Q40. The products of the reaction of sodium fluoride with concentrated sulfuric acid can be predicted by considering the trends for the other sodium halides. Which gas or gases form when sodium fluoride reacts with concentrated sulfuric acid?
A hydrogen fluoride only
B hydrogen fluoride and fluorine only
C hydrogen fluoride and sulfur dioxide only
D hydrogen fluoride, fluorine and sulfur dioxide only
Use this space for any rough working.
Anything you write in this space will gain no credit.
(Total for question = 1 mark)
Q41. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which silver halides are soluble in concentrated aqueous ammonia?
A AgBr and AgI
B AgCl and AgI
C AgCl and AgBr
D AgCl only
(Total for question = 1 mark)
Q42. For each question, select one answer from A to D and put a cross in the box .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Four tests used to identify ions are shown:
1 flame test
2 addition of acidified barium nitrate solution
3 addition of acidified silver nitrate solution
4 addition of sodium hydroxide solution, then testing any gas with indicator paper
Which tests could be used to positively identify the ions in ammonium chloride?
A 1 and 2
B 1 and 3
C 2 and 4
D 3 and 4
(Total for question = 1 mark)
Q43. Which test is used to show that sodium chloride solution contains chloride ions? (1)
A damp blue litmus paper turns red
B damp blue litmus paper is bleached
C dilute hydrochloric acid followed by silver nitrate solution gives a white precipitate
D dilute nitric acid followed by silver nitrate solution gives a white precipitate
(Total for question = 1 mark)
Q44. Answer the question with a cross in the box you think is correct .
If you change your mind about an answer, put a line through the box and then mark your new answer with a cross .
Which of these increases as Group 7 is descended?
A oxidising ability of the molecular halogens
B reducing ability of the halide ions
C electrostatic attraction between the nucleus and outer shell of electrons
D electronegativity of the halogen atoms
(Total for question = 1 mark)
If you need the markscheme, including the examiners' reports for each question, and more exam and teaching materials on this topic, contact me through the contact page