DP Chemistry (last assessment 2024)

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Question 22M.2.hl.TZ2.3b(i)

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Date May 2022 Marks available [Maximum mark: 2] Reference code 22M.2.hl.TZ2.3b(i)
Level hl Paper 2 Time zone TZ2
Command term Deduce Question number b(i) Adapted from N/A
b(i).
[Maximum mark: 2]
22M.2.hl.TZ2.3b(i)

Standard electrode potential values, E⦵, can be used to predict spontaneity.

(b(i))

Molten zinc chloride undergoes electrolysis in an electrolytic cell at 450 °C.

Deduce the half-equations for the reaction at each electrode.

 

[2]

Markscheme

Cathode (negative electrode):

Zn2+ + 2e− → Zn (l) ✔

 

Anode (positive electrode):

2Cl− → Cl2 (g) + 2e−
OR
Cl− → ½ Cl2 (g) + e− ✔

Examiners report

3(bi)/(bii) Answers to both these questions revealed that many candidates struggle to conceptualize the equations that describe electrolysis. The question asked for products of the easiest case of electrolysis, a molten salt. However, many candidates proposed oxidation or reduction equations at both electrodes, or Zn and Cl2 (with no charge) as the initial species rather than the product; the average mark was 1.2/2 as only 55% answered correctly.

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