DP Chemistry (last assessment 2024)

Question 20N.2.hl.TZ0.e(i)

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

e(i).

[Maximum mark: 2]

20N.2.hl.TZ0.e(i)

Chlorine undergoes many reactions.

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

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

Another good example of candidates being well rehearsed in calculations with 90% earning 2/2 on this question of calculation percentage by mass composition.

Syllabus sections

Core

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

Core » Topic 1: Stoichiometric relationships

Question 20N.2.hl.TZ0.e(i)

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