DP Chemistry (last assessment 2024)

Question 20N.3.hl.TZ0.a(i)

Date	November 2020	Marks available	[Maximum mark: 1]	Reference code	20N.3.hl.TZ0.a(i)
Level	hl	Paper	3	Time zone	TZ0
Command term	Calculate	Question number	a(i)	Adapted from	N/A

a(i).

[Maximum mark: 1]

20N.3.hl.TZ0.a(i)

A mixture of $0.100 mol$ ethanal, $0.100 mol$ ethanol and $0.200 mol$ ethanoic acid is fractionally distilled.

Calculate the mole fraction of ethanal in the mixture.

[1]

Markscheme

$« χ_{ethanal} = \frac{0.100}{0.100 + 0.100 + 0.200} = » 0.250$ ✔

Accept “ $25 %$ ”.

Examiners report

This question involving Raoult's Law was very well answered and most were able to calculate the mole fraction of ethanal in the mixture (0.250) and the corresponding vapour pressure of ethanal above the liquid mixture at 20 °C (25.3 kPa). There was one G2 comment on this question. One teacher stated that the diagram shows four fractions but the stem of the question specifically states only three components and hence the fourth test tube is not required. The teacher commented that some students may have been distracted by this.

Syllabus sections

Core

Core » Topic 1: Stoichiometric relationships » 1.3 Reacting masses and volumes

Core » Topic 1: Stoichiometric relationships

Question 20N.3.hl.TZ0.a(i)

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