Redox Question Paper Level Subject Exam oard Topic Sub-Topic ooklet O Level hemistry ambridge International Examinations hemical Reactions Redox Question Paper Time llowed: 52 minutes Score: /43 Percentage: /100
1 Which equation does not represent a redox reaction? 2NH 3 + H 2 SO 4 (NH 4 ) 2 SO 4 2SO 2 + O 2 2SO 3 2KI + l 2 2Kl + I 2 Zn + H 2 SO 4 ZnSO 4 + H 2 2 Gaseous compound X is an oxidising agent. X is bubbled through separate solutions of aqueous potassium iodide and acidified potassium manganate(vii). X X aqueous potassium iodide acidified potassium manganate(vii) Which row shows the colour changes when X is bubbled through these two solutions? aqueous potassium iodide brown to colourless brown to colourless colourless to brown colourless to brown acidified potassium manganate(vii) no change no change
3 The equation shows a redox reaction between iron(ii) chloride and chlorine gas. 2Fel 2 + l 2 2Fel 3 Which equation describes the reduction process in this reaction? 2l l 2 + 2e l 2 + 2e 2l Fe 2+ Fe 3+ + e Fe 3+ + e Fe 2+ 4 How is a calcium ion, a 2+, formed from a calcium atom? by gaining two electrons by gaining two protons by losing two electrons by losing two protons 5 In which reaction is nitric acid acting as an oxidising agent? u + 4HNO 3 u(no 3 ) 2 + 2H 2 O + 2NO 2 uo + 2HNO 3 u(no 3 ) 2 + H 2 O Na 2 O 3 + 2HNO 3 2NaNO 3 + H 2 O + O 2 NaOH + HNO 3 NaNO 3 + H 2 O
6 queous potassium iodide, KI(aq), can be used as a test reagent in redox reactions. Iodide ions are readily X. positive result for the test is when the solution changes colour from Y to Z. Which words correctly complete gaps X, Y and Z? X Y Z oxidised brown colourless oxidised colourless brown reduced brown colourless reduced colourless brown 7 Which ionic equation represents a redox reaction? g + + l gl a 2+ + 2 SO4 aso 4 H + + OH H 2 O Zn + u 2+ Zn 2+ + u 8 The equation shows the reaction for the formation of sulfur trioxide using a catalyst. 2SO 2 (g) + O 2 (g) 2SO 3 (g) H = 197 kj / mol Which change in reaction conditions would produce more sulfur trioxide? adding more catalyst decreasing the pressure increasing the temperature removing some sulfur trioxide
9 Equations for reactions of iron and iron compounds are shown. Fe + 2Hl Fel 2 + H 2 2Fel 2 + l 2 2Fel 3 FeSO 4 + Mg Fe + MgSO 4 FeSO 4 + 2NaOH Fe(OH) 2 + Na 2 SO 4 How many of these are redox reactions? 1 2 3 4 10 Which statement describes the conversion of magnesium atoms to magnesium ions? The change is reduction, because there has been a gain of electrons. The change is oxidation, because there has been a loss of electrons. The change is reduction, because there has been a loss of electrons. The change is oxidation, because there has been a gain of electrons. 11 Which colour change occurs when ethanol is added to a small quantity of warm, acidified potassium dichromate(vi)? orange to colourless orange to green purple to green 12 queous copper(ii) sulfate is electrolysed using copper electrodes. Which equation represents the reaction taking place at the anode (positive electrode) in this electrolysis? u(s) u 2+ (aq) + 2e SO 4 2 (aq) SO 2 (g) + O 2 (g) + 2e u 2+ (aq) + 2e u(s) 4OH (aq) 2H 2 O(l) + O 2 (g) + 4e
13 In which equation is the underlined element reduced? uso 4 (aq) + Mg(s) u(s) + MgSO 4 (aq) 2Fel 2(s) + l 2(g) 2Fel 3(s) 2SO 2 (g) + O 2 (g) 2SO 3 (g) Zn(s) + H 2 SO 4 (aq) ZnSO 4 (aq) + H 2 (g) 14 n atom of which element gains three electrons when it forms an ion? aluminium iron nitrogen silicon 15 Which method of preparation of magnesium sulfate is an example of a redox reaction? Mg + H 2 SO 4 MgSO 4 + H 2 MgO + H 2 SO 4 MgSO 4 + H 2 O Mg(OH) 2 + H 2 SO 4 MgSO 4 + 2H 2 O MgO 3 + H 2 SO 4 MgSO 4 + H 2 O + O 2 16 What is the function of silica, SiO 2, in the equation shown below? ao + SiO 2 asio 3 a basic oxide a reducing agent an acidic oxide an oxidising agent
17 What happens when zinc foil is placed in an aqueous solution of copper(ii) sulfate? opper(ii) ions are oxidised. There is no reaction. Zinc atoms are oxidised. Zinc sulfate is precipitated. 18 Sulfur dioxide reacts with aqueous bromine according to the following equation. Which element has been oxidised? SO 2 (g) + r 2 (aq) + 2H 2 O(l) H 2 SO 4 (aq) + 2Hr(aq) bromine hydrogen oxygen sulfur 19 The diagram shows steel wool inside a test-tube. The test-tube is inverted in water, trapping air inside. What will be the water level inside the tube after several days? steel wool air water level at beginning of experiment
20 Which reaction does not involve either oxidation or reduction? H 4 (g) + 2O 2 (g) O 2 (g) + 2H 2 O(g) u 2+ (aq) + Zn(s) u(s) + Zn 2+ (aq) uo(s) + H 2 SO 4 (aq) uso 4 (aq) + H 2 O(l) Zn(s) + H 2 SO 4 (aq) ZnSO 4 (aq) + H 2 (g) 21 Which equation in the blast furnace extraction of iron is not a redox reaction? ao 3 ao + O 2 2 + O 2 2O + O 2 2O Fe 2 O 3 + 3O 2Fe + 3O 2 22 What is not an example of oxidation? converting iron(iii) salts into iron(ii) salts converting magnesium atoms into magnesium ions dissolving of a copper anode during electrolysis liberating chlorine from a chloride 23 Which row in the table describes the processes occurring at the electrodes when molten sodium chloride is electrolysed?
24 The ionic equation shows the reaction between potassium iodide and iron(iii) chloride. 2Fe 3+ (aq) + 2I (aq) 2Fe 2+ (aq) + I 2 (aq) Which terms describe the changes to the iron(iii) ions and iodide ions? 25 Which ionic equation represents the reaction taking place at the anode during the electrolysis of molten aluminium oxide? l 3+ + 3e l 2l 3+ + 3O 2 l 2O 3 O 2 2e O 2 2O 2 4e O 2 26 colourless gas is passed into each of three different solutions. The results for each solution are shown in the table. solution potassium iodide acidified potassium dichromate(vi) acidified potassium manganate(vii) result stays colourless orange to green What is the colourless gas? an acid an alkali an oxidising agent a reducing agent
27 In which reaction is sulphur dioxide acting as an oxidising agent? SO 2 + 2H 2 O + l 2 H 2 SO 4 + 2Hl SO 2 + 2NaOH Na 2 SO 3 + H 2 O 2SO 2 + O 2 2SO 3 SO 2 + 2H 2 S 2H 2 O + 3S 28 Which process does not involve either oxidation or reduction? formation of ammonium sulphate from ammonia and sulphuric acid formation of nitrogen monoxide from ammonia formation of sulphuric acid from sulphur formation of zinc from zinc blende (ZnS) 29 queous copper(ii) sulphate is electrolysed using inert electrodes as shown. carbon electrode carbon electrode aqueous copper(ii) sulphate Which ionic equations show the reactions at the electrodes? 1 2 3 4 u 2+ + 2e u u u 2+ + 2e 2 + + 2e H 2 4O 2H 2 O + O 2 + 4e 1 and 2 only 1 and 4 only 2 and 3 only 3 and 4 only
30 In which change is the nitrogen reduced? NH 3 to NO NH 3 to NO 3 N 2 to NH 3 N 3 to N 2 31 The reaction between hydrogen sulphide and sulphur dioxide is represented by the equation shown. What occurs in this reaction? 2H 2 S(g) + SO 2 (g) 2H 2 O(l) + 3S(s) reactants products oth reactants are reduced. The two reactants are neither oxidised nor reduced. Hydrogen sulphide is oxidised and sulphur dioxide is reduced. Sulphur dioxide is oxidised and hydrogen sulphide is reduced. 32 Which change is an example of oxidation? chloride ions to chlorine atoms copper(ii) ions to copper atoms iron(iii) ions to iron(ii) ions oxygen atoms to oxide ions 33 Which of the reactions X, Y and Z involve oxidation? ethanol H OH 2 5 X ethyl ethanoate H O H 3 2 2 5 Z ethanoic acid H O H 3 2 Y sodium ethanoate H O Na 3 2 X only X and Y Y only Y and Z
34 Which compound, when added to aqueous iron(ii) sulphate, takes part in a redox reaction? ammonia barium chloride acidified potassium dichromate(vi) sodium hydroxide 35 The experiment is set up as shown and left until there is no further change. water What is observed? purple crystal of potassium manganate(vii) a colourless layer below a purple layer a colourless liquid with the purple crystal unchanged a purple layer below a colourless layer a uniformly purple solution 36 colourless gas is passed into each of three different solutions. The results are shown in the table. solution of potassium iodide acidified potassium dichromate(vi) acidified potassium manganate(vii) result stays colourless orange to green What is the colourless gas? an acid an alkali an oxidising agent a reducing agent
37 Separate samples of hydrogen peroxide are added to aqueous potassium iodide and to acidified potassium dichromate(vi). The iodide ions are oxidised and dichromate(vi) ions are reduced. What colour changes are seen? potassium iodide colourless to brown brown to colourless colourless to brown brown to colourless acidified potassium dichromate(vi) orange to green orange to green 38 In which line in the table is all the information correct? reaction at electrode electrode product 2X X 2 + 2e cathode metal X + + e X anode metal 2X X 2 + 2e anode non-metal X + + e X cathode non-metal 39 Small portions of aqueous potassium iodide and of acidified, aqueous potassium manganate(vii) were added to four solutions. The colour changes seen are shown in the table. solution number potassium iodide potassium manganate(vii) 1 2 3 4 colourless to red colourless to red no change no change no change no change Which solutions contained an oxidising agent? 1 only 1 and 2 only 1 and 3 only 2 and 4 only
40 ilute sulphuric acid is electrolysed using inert electrodes. Which equation represents the reaction at the anode (+ve)? O 2 2 O 2 + 2e + 2H + 2e H 2 4OH O 2 + 2H 2 O + 4e SO 2 4 O 2 + SO 2 + 2e 41 Which series of changes includes both oxidation and reduction? O O 2 PbO 2 PbO Pb N 2 NH 3 NO 2 H 2 2 H 4 2 H 6 42 Substance X liberates iodine from aqueous potassium iodide and decolourises acidified aqueous potassium manganate(vii). How is the behaviour of X described? as an oxidising agent only as an oxidising agent and a reducing agent as neither an oxidising agent nor a reducing agent as a reducing agent only 43 When acidified potassium manganate(vii) is reduced, which colour change occurs? from colourless to purple from green to orange from orange to green from