DP Chemistry (last assessment 2024)

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Question 17N.2.hl.TZ0.e

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Date November 2017 Marks available [Maximum mark: 4] Reference code 17N.2.hl.TZ0.e
Level hl Paper 2 Time zone TZ0
Command term State and explain Question number e Adapted from N/A
e.
[Maximum mark: 4]
17N.2.hl.TZ0.e

Consider the following half-cell reactions and their standard electrode potentials.

State and explain the products of electrolysis of a concentrated aqueous solution of sodium chloride using inert electrodes. Your answer should include half-equations for the reaction at each electrode.

[4]

Markscheme

Positive electrode (anode):
2Cl– (aq) → Cl2 (g) + 2e–

Cl– oxidized because higher concentration

OR

electrode potential/E depends on concentration

OR

electrode potential values «of H2O and Cl–» are close

Negative electrode (cathode):
2H2O (l) + 2e– → H2 (g) + 2OH– (aq)

OR

2H+ (aq) + 2e– → H2 (g)

H2O/H+ reduced because Na+ is a weaker oxidizing agent

OR

Na+ not reduced to Na in water

OR

H+ easier to reduce than Na+
OR

H lower in activity series «than Na»

Accept ⇌ .

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