DP Chemistry (last assessment 2024)

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Question 22M.2.hl.TZ2.4d(ii)

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Date May 2022 Marks available [Maximum mark: 1] Reference code 22M.2.hl.TZ2.4d(ii)
Level hl Paper 2 Time zone TZ2
Command term Justify, Predict Question number d(ii) Adapted from N/A
d(ii).
[Maximum mark: 1]
22M.2.hl.TZ2.4d(ii)

Hydrogen and iodine react to form hydrogen iodide.

H2 (g) + I2 (g) ⇌ 2HI (g)

Consider the reaction of hydrogen with solid iodine.

H2 (g) + I2 (s) ⇌ 2HI (g)     ΔH⦵ = +53.0 kJ mol−1

(d(ii))

Predict, giving a reason, how the value of the ΔS⦵reaction would be affected if I2 (g) were used as a reactant.

[1]

Markscheme

ΔS⦵reaction lower/less positive AND same number of moles of gas

OR

ΔS⦵reaction lower/less positive AND a solid has less entropy than a gas ✔

Examiners report

Some candidates confused the entropy change in this situation with absolute entropy of a solid and gas, or having realised that entropy would decrease lacked clarity in their explanations and lost the mark.

4(d)(ii)-(d)(iv): marks were lost due to inconsistency of units throughout, i.e., not because answers were given in different units to those required, but because candidates failed to convert all data to the same unit for calculations.

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