DP Chemistry (last assessment 2024)

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Question 22M.2.sl.TZ2.5a

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Date May 2022 Marks available [Maximum mark: 2] Reference code 22M.2.sl.TZ2.5a
Level sl Paper 2 Time zone TZ2
Command term Deduce Question number a Adapted from N/A
a.
[Maximum mark: 2]
22M.2.sl.TZ2.5a

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

(a)

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

The half-equations were often incorrect. The average mark was 0.8 out of 2, and the correlation to high scoring candidates was strong as expected. Many candidates started the half-equations with the elements and gave the ions as products. We also saw some scripts with Cl instead of Cl2 as the product. Some of the candidates thought the zinc ion was Zn+ instead of Zn2+. Some candidates reversed the anode and cathode equations earning only 1 of the 2 marks.

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