Unit 20 Oxidation and reduction Activity 20.1 Investigating redox reactions Reference in textbook: Section S

Unit 20Oxidation and reduction Activity 20.1 Investigating redox reactions (S) Observations A Reaction between aqueous bromine and iron(II) sulphate solution 15

Unit 20Oxidation and reduction Activity 20.1 Investigating redox reactions (S) BReaction between acidified potassium permanganate solution and iron(II) sulphate solution 16The colour of the acidified potassium permanganate solution changes from _______________ to _______________. C Reaction between iron(III) sulphate solution and potassium iodide solution 17The colour of the potassium iodide solution changes from _______________ to _______________. D Reaction between acidified potassium dichromate solution and sodium sulphite solution 18The colour of the acidified potassium dichromate solution changes from _______________ to _______________. purplecolourless brown orangegreen

Unit 20Oxidation and reduction Activity 20.1 Investigating redox reactions (S) Discussion A Reaction between aqueous bromine and iron(II) sulphate solution 19a)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 20.1 Investigating redox reactions (S) B Reaction between acidified potassium permanganate solution and iron(II) sulphate solution 20a)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 20.1 Investigating redox reactions (S) C Reaction between iron(III) sulphate solution and potassium iodide solution 21a)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 20.1 Investigating redox reactions (S) D Reaction between acidified potassium dichromate solution and sodium sulphite solution 22a)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 20.1 Investigating redox reactions (S) Conclusion 23Complete the following table. Redox reaction between aqueous bromine and iron(II) sulphate solution bromine is ( oxidized / reduced ) to ___________ ions; iron(II) ions are ( oxidized / reduced ) to ___________ ions Redox reaction between acidified potassium permanganate solution and 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 potassium iodide solution iron(III) ions are ( oxidized / reduced ) to ___________ ions; iodide ions are ( oxidized / reduced ) to ___________ ions Redox reaction between acidified potassium dichromate solution and sodium sulphite solution sulphite ions are ( oxidized / reduced ) to ___________ ions; dichromate ions are ( oxidized / reduced ) to _______________ ions bromide iron(III) iron(II) iodine manganese(II) sulphate chromium(III)

Unit 20Oxidation and reduction Activity 20.1 Investigating redox reactions (S) Question 24In 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 Fe 2+ (aq)  Fe 3+ (aq) + e – Br 2 (aq) + 2e –  2Br – (aq) 2Fe 2+ (aq) + Br 2 (aq)  2Fe 3+ (aq) + 2Br – (aq)

Unit 20Oxidation and reduction Activity 20.1 Investigating redox reactions (S) 25In 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 Fe 2+ (aq)  Fe 3+ (aq) + e – MnO 4 – (aq) + 8H + (aq) + 5e –  Mn 2+ (aq) + 4H 2 O(l) MnO 4 – (aq) + 5Fe 2+ (aq) + 8H + (aq)  Mn 2+ (aq) + 5Fe 3+ (aq) + 4H 2 O(l)

Unit 20Oxidation and reduction Activity 20.1 Investigating redox reactions (S) 26In 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)  I 2 (aq) + 2e – Fe 3+ (aq) + e –  Fe 2+ (aq) 2Fe 3+ (aq) + 2I – (aq)  2Fe 2+ (aq) + I 2 (aq)

Unit 20Oxidation and reduction Activity 20.1 Investigating redox reactions (S) 27In 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 SO 3 2– (aq) + H 2 O(l)  SO 4 2– (aq) + 2H + (aq) + 2e – Cr 2 O 7 2– (aq) + 14H + (aq) + 6e –  2Cr 3+ (aq) + 7H 2 O(l) Cr 2 O 7 2– (aq) + 8H + (aq) + 3SO 3 2– (aq)  2Cr 3+ (aq) + 3SO 4 2– (aq) + 4H 2 O(l)