DP Chemistry (last assessment 2024)

Question 20N.2.hl.TZ0.e

Date	November 2020	Marks available	[Maximum mark: 2]	Reference code	20N.2.hl.TZ0.e
Level	hl	Paper	2	Time zone	TZ0
Command term	Calculate	Question number	e	Adapted from	N/A

[Maximum mark: 2]

20N.2.hl.TZ0.e

An equation for the combustion of propane is given below.

C₃H₈(g) + 5O₂(g) 3CO₂(g) + 4H₂O(g)

Calculate the standard Gibbs free energy change, $∆ G^{⦵}$ , in $kJ$ , for the reaction at 5 °C, using your answers to (b) and (d). Use section 1 of the data booklet.

(If you did not obtain an answer to (b) or (d) use values of $- 1952 kJ$ and $+ 113 J K^{- 1}$ respectively, although these are not the correct answers.)

[2]

Markscheme

$« T = 5 + 273 = » 278 K$ ✔

$« {ΔG}^{⦵} = - 2043 kJ - (278 K \times 0.102 kJ K^{- 1}) = » - 2071 « kJ »$ ✔

Award [2] for correct final answer.

Examiners report

ΔG^ө calculations were also well done, with some not seeing that specific units were to be used.

Syllabus sections

Additional higher level (AHL)

Additional higher level (AHL) » Topic 15: Energetics/thermochemistry » 15.2 Entropy and spontaneity

Additional higher level (AHL) » Topic 15: Energetics/thermochemistry

Question 20N.2.hl.TZ0.e

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