Unit 20 Oxidation and reduction

Activity 20.1Investigating redox reactions

Reference in textbook: Section 20.10

S

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

ObservationsA Reaction between aqueous bromine and iron(II) sulphate solution15

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

B Reaction between acidified potassium permanganate solution and iron(II)

sulphate solution

16 The colour of the acidified potassium permanganate solution changes from _______________ to _______________ .

C Reaction between iron(III) sulphate solution and potassium iodide solution

17 The colour of the potassium iodide solution changes from _______________to _______________ .

D Reaction between acidified potassium dichromate solution and sodium sulphite solution

18 The colour of the acidified potassium dichromate solution changes from _______________ to _______________ .

purple colourless

colourlessbrown

orange green

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

DiscussionA Reaction between aqueous bromine and iron(II) sulphate solution19 a) What happens to the iron(II) ions in the reaction?

___________________________________________________________

b) What evidence do you have for this?

___________________________________________________________

___________________________________________________________

___________________________________________________________

c) What happens to the aqueous bromine?

___________________________________________________________

The iron(II) ions are oxidized to iron(III) ions.

The bromine is reduced to bromide ions.

The reaction mixture gives a reddish brown precipitate with

dilute sodium hydroxide solution. This shows the presence of

iron(III) ions.

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

B Reaction between acidified potassium permanganate solution and iron(II) sulphate solution

20 a) What happens to the permanganate ions in the reaction?

___________________________________________________________

b) What evidence do you have for this?

___________________________________________________________

___________________________________________________________

c) What happens to the iron(II) ions?

___________________________________________________________

The permanganate ions are reduced to manganese(II) ions.

The purple potassium permanganate solution becomes

colourless.

The iron(II) ions are oxidized to iron(III) ions.

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

C Reaction between iron(III) sulphate solution and potassium iodide solution

21 a) What happens to the iodide ions in the reaction?

_____________________________________________________________

b) What evidence do you have for this?

_____________________________________________________________

_____________________________________________________________

c) What happens to the iron(III) ions?

_____________________________________________________________

The iodide ions are oxidized to iodine.

The reaction mixture becomes brown (or yellow) in colour.

This shows the presence of iodine.

The iron(III) ions are reduced to iron(II) ions.

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

D Reaction between acidified potassium dichromate solution and sodium sulphite solution

22 a) What happens to the dichromate ions in the reaction?

______________________________________________________________

b) What evidence do you have for this?

______________________________________________________________

______________________________________________________________

c) What happens to the sulphite ions?

______________________________________________________________

The dichromate ions are reduced to chromium(III) ions.

The reaction mixture becomes green in colour. This shows

the presence of chromium(III) ions.

The sulphite ions are oxidized to sulphate ions.

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

Conclusion

23 Complete the following table.

Redox reaction between aqueousbromine and iron(II) sulphate solution

bromine is ( oxidized / reduced ) to ___________ ions; iron(II) ions are ( oxidized / reduced ) to ___________ ions

Redox reaction between acidifiedpotassium permanganate solutionand iron(II) suphate solution

iron(II) ions are ( oxidized / reduced ) to ___________ ions; permanganate ions are ( oxidized / reduced ) to ______________ ions

Redox reaction between iron(III)sulphate solution and potassiumiodide solution

iron(III) ions are ( oxidized / reduced ) to ___________ ions; iodide ions are ( oxidized / reduced ) to ___________ ions

Redox reaction between acidifiedpotassium dichromate solution and sodium sulphite solution

sulphite ions are ( oxidized / reduced ) to ___________ ions; dichromate ions are ( oxidized / reduced ) to _______________ ions

bromide iron(III)

iron(III)

iron(II)iodine

manganese(II)

sulphatechromium(III)

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

Question24 In the redox reaction between aqueous bromine and iron(II) sulphate solution:

a) The oxidizing agent is __________________________ .

The reducing agent is __________________________ .

b) Write an ionic half-equation for the oxidation process.

______________________________________________________

Write an ionic half-equation for the reduction process.

______________________________________________________

Write a balanced redox equation for the reaction.

______________________________________________________

aqueous bromine

iron(II) sulphate solution

Fe2+(aq) Fe3+(aq) + e–

Br2(aq) + 2e– 2Br–(aq)

2Fe2+(aq) + Br2(aq) 2Fe3+(aq) + 2Br–(aq)

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

25 In the redox reaction between acidified potassium permanganate solution and iron(II) sulphate solution:a) The oxidizing agent is ______________________________________________ .

The reducing agent is ___________________________ .

b) Write an ionic half-equation for the oxidation process.

________________________________________________________________

Write an ionic half-equation for the reduction process.

________________________________________________________________

Write a balanced redox equation for the reaction.

________________________________________________________________

acidified potassium permanganate solution

iron(II) sulphate solution

Fe2+(aq) Fe3+(aq) + e–

MnO4–(aq) + 8H+(aq) + 5e– Mn2+(aq) + 4H2O(l)

MnO4–(aq) + 5Fe2+(aq) + 8H+(aq) Mn2+(aq) + 5Fe3+(aq) + 4H2O(l)

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

26 In the redox reaction between iron(III) sulphate solution and potassium iodide solution:a) The oxidizing agent is ___________________________ .

The reducing agent is ____________________________ .

b) Write an ionic half-equation for the oxidation process.

________________________________________________________

Write an ionic half-equation for the reduction process.

________________________________________________________

Write a balanced redox equation for the reaction.

________________________________________________________

iron(III) sulphate solution

potassium iodide solution

2I–(aq) I2(aq) + 2e–

Fe3+(aq) + e– Fe2+(aq)

2Fe3+(aq) + 2I–(aq) 2Fe2+(aq) + I2(aq)

Unit 20Oxidation and

reduction

Activity 20.1Investigating redox reactions (S)

27 In the redox reaction between acidified potassium dichromate solution and sodium sulphite solution:a) The oxidizing agent is _________________________________________ .

The reducing agent is _____________________________ .

b) Write an ionic half-equation for the oxidation process.

____________________________________________________________________

Write an ionic half-equation for the reduction process.

____________________________________________________________________

Write a balanced redox equation for the reaction.

____________________________________________________________________

acidified potassium dichromate solution

sodium sulphite solution

SO32–(aq) + H2O(l) SO4

2–(aq) + 2H+(aq) + 2e–

Cr2O72–(aq) + 14H+(aq) + 6e– 2Cr3+(aq) + 7H2O(l)

Cr2O72–(aq) + 8H+(aq) + 3SO3

2–(aq) 2Cr3+(aq) + 3SO42–(aq) + 4H2O(l)