Redox Tutorial Questions

1. An oxidising agent

A. Accepts electrons

B. Donates electrons

C. Accepts protons

D. Donates protons

2. A reducing agent

A. Accepts electrons

B. Donates electrons

C. Accepts protons

D. Donates protons

3.

Mg(s) + Cu2+

(aq) Mg2+

(aq) + Cu(s)

In the above reaction, the oxidising agent is

A. Mg(s)

B. Cu2+

(aq)

C. Mg2+

(aq)

D. Cu(s)

4.

Fe3+

(aq) + 2I¯(aq) Fe2+

(aq) + I2(s)

In the above reaction, the reducing agent is

A. Fe3+

(aq)

B. I¯(aq)

C. Fe2+

(aq)

D. I2(s)

5. The correct redox equation for the reaction of bromine with a solution containing

iodide ions is

A. Br2(l) + I¯(aq) 2Br¯(aq) + I2(s)

B. Br2(l) + 2I¯(aq) Br¯(aq) + I2(s)

C. Br2(l) + 2I¯(aq) 2Br¯(aq) + I2(s)

D. Br2(l) + 2I¯(aq) Br¯(aq) + I2(s)

6. The correct redox equation for the reaction of acidified MnO4¯ (aq) and Fe2+

(aq) is

A. Fe2+

(aq) + MnO4¯ (aq) + 8H+(aq) Mn

2+(aq) + 4H2O(l) + Fe

3+(aq)

B. 5Fe2+

(aq) + MnO4¯ (aq) + 8H+(aq) Mn

2+(aq) + 4H2O(l) + 5Fe

3+(aq)

C. 5Fe2+

(aq) + 2MnO4¯ (aq) + 8H+(aq) 2Mn

2+(aq) + 4H2O(l) + 5Fe

3+(aq)

D. Fe2+

(aq) + 5MnO4¯ (aq) + 8H+(aq) 5Mn

2+(aq) + 4H2O(l) + Fe

3+(aq)

7. H2O2(aq) + 2H+ + ne¯ 2H2O(l)

The value of n in the above equation should be

A. 1

B. 2

C. 3

D. 4

Questions 8 to 11 refer to the equation

wIO3¯ + xH+ + ye¯ I2 + zH2O

8. The value for w is

A. 1

B. 2

C. 3

D. 4

9. The value for x is

A. 4

B. 6

C. 12

D. 18

10. The value for y is

A. 6

B. 8

C. 10

D. 12

11. The value for z is

A. 2

B. 4

C. 6

D. 8

12. Iron (II) ions and dichromate ions react together according to the following

equation

6Fe2+

(aq) + Cr2O7¯ (aq) + 14H+(aq) 2Cr

3+(aq) + 7H2O(l) + 6Fe

3+(aq)

If 50 cm3 of 0.1 mol l

-1 dichromate solution was found to react exactly with 30 cm

3 of

iron (II) solution, the concentration of the iron (II) is

A. 0.1 mol l-1

B. 0.6 mol l-1

C. 1.0 mol l-1

D. 1.6 mol l-1

13. Iron (II) ions and permanganate ions react together in a redox reaction.

If 100 cm3 of 0.02 mol l

-1 permanganate solution was found to react exactly with 20

cm3 of iron (II) solution, the concentration of the iron (II) is

A. 0.02 mol l-1

B. 0.1 mol l-1

C. 0.2 mol l-1

D. 0.5 mol l-1

14. In acid solution it is possible to convert bromate ions to bromide ions i.e.

BrO3 (aq) Br2 (aq)

To balance this ion electron equation the number of electrons needed is

A. 6

B. 8

C. 10

D. 12

15. Permanganate ions will in acid solution oxidise iron (II) ions to iron (III) ions.

The number of moles of iron (II) ions oxidised by one mole of permanganate ions is

A. 1

B. 2.5

C. 3

D. 5

16. MnO4 + 8H+ + 5e

Mn

2+ + 4H2O

Fe2+

Fe3+

+ e

Combine the above two ion electron equations to give the redox equation for

permanganate ion oxidising iron (II) to iron (III). In an experiment it was found that

25 cm3 of acidified potassium permanganate solution oxidised 10 cm

3 of iron (II)

sulphate solution of concentration 0.04 mol l-1

. Calculate the concentration of the

potassium permanganate solution.

17. Oxalic acid is found in rhubarb leaves. The concentration of an oxalic acid

solution can be found by titration with potassium permanganate solution.

The ion - electron equation for oxalic acid is

C2H2O4 2CO2 + 2H+

+ 2e

In an experiment a pupil titrated 25cm3 samples of the oxalic acid solution, using 0.02

mol l-1

potassium permanganate solution in a burette. She obtained the following

results

rough first second

Second burette

reading / cm3

12.9 25.3 37.7

First burette

reading / cm3

0.0 12.9 25.3

Titre / cm3

a) Calculate the titre values

b) Calculate the average titre

c) Write the ion – electron half equation for the reduction of permanganate ion.

d) Use your answer to (c) and the ion – electron half equation for oxalic acid to

write the redox equation for the reaction.

e) Use your answer to (b) to calculate how many moles of permanganate reacted.

f) Use your answers to (b) and (d) to calculate how many moles of oxalic acid

was present in the 25 cm3 samples.

g) Calculate the concentration of the oxalic acid solution in mol l-1

.

Redox Reactions

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