DP Chemistry (last assessment 2024)

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Question 19M.2.hl.TZ2.4e(ii)

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Date May 2019 Marks available [Maximum mark: 1] Reference code 19M.2.hl.TZ2.4e(ii)
Level hl Paper 2 Time zone TZ2
Command term Deduce Question number e(ii) Adapted from N/A
e(ii).
[Maximum mark: 1]
19M.2.hl.TZ2.4e(ii)

Rhenium, Re, was the last element with a stable isotope to be isolated.

Rhenium forms salts containing the perrhenate(VII) ion, ReO4−.

(e(ii))

Deduce the coefficients required to complete the half-equation.

ReO4− (aq) + ____H+ (aq) + ____e− ⇌ [Re(OH)2]2+ (aq) + ____H2O (l)        Eθ = +0.36 V

[1]

Markscheme

ReO4− (aq) + 6H+ (aq) + 3e− ⇌ [Re(OH)2]2+ (aq) + 2H2O (l)    [✔]

Examiners report

Surprisingly, a great number of students were unable to balance this simple half-equation that was given to them to avoid difficulties in recall of reactants/products.

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