DP Chemistry (last assessment 2024)

Question 20N.2.sl.TZ0.1e(i)

Date	November 2020	Marks available	[Maximum mark: 2]	Reference code	20N.2.sl.TZ0.1e(i)
Level	sl	Paper	2	Time zone	TZ0
Command term	Calculate	Question number	e(i)	Adapted from	N/A

e(i).

[Maximum mark: 2]

20N.2.sl.TZ0.1e(i)

Chlorine undergoes many reactions.

${CCl}_{2} F_{2}$ is a common chlorofluorocarbon, $CFC$ .

(e(i))

Calculate the percentage by mass of chlorine in ${CCl}_{2} F_{2}$ .

[2]

Markscheme

$« M ({CCl}_{2} F_{2}) = » 120.91 « g {mol}^{- 1} »$ ✔

$\frac{2 \times 35.45 g {mol}^{- 1}}{120.91 g {mol}^{- 1}} \times 100 % = » 58.64 « % »$ ✔

Award [2] for correct final answer.

Examiners report

This was the highest scoring question in the paper. The majority of candidates were able to calculate the percentage by mass of chlorine in CCl₂F₂. Mistakes included incorrect rounding and arithmetic errors.

Syllabus sections

Core

Core » Topic 1: Stoichiometric relationships » 1.2 The mole concept

Core » Topic 1: Stoichiometric relationships

Question 20N.2.sl.TZ0.1e(i)

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