DP Chemistry (last assessment 2024)

Question 20N.2.hl.TZ0.5d

Date	November 2020	Marks available	[Maximum mark: 1]	Reference code	20N.2.hl.TZ0.5d
Level	hl	Paper	2	Time zone	TZ0
Command term	Calculate	Question number	d	Adapted from	N/A

[Maximum mark: 1]

20N.2.hl.TZ0.5d

A student performs a titration to determine the concentration of ethanoic acid, ${CH}_{3} COOH$ , in vinegar using potassium hydroxide.

(d)

Calculate the $K_{b}$ of the conjugate base of ethanoic acid using sections 2 and 21 of the data booklet.

[1]

Markscheme

$« K_{a} = 10^{- 4.76} = 1.7 \times 10^{- 5} »$
$« K_{w} = K_{a} \cdot K_{b} = 1.0 \times 10^{- 14} = 1.7 \times 10^{- 5} \times K_{b} »$
$« K_{b} = » 5.8 \times 10^{- 10}$ ✔

Accept answers between $5.7 - 5.9 \times 10^{- 10}$ .

Syllabus sections

Core

Additional higher level (AHL)

Additional higher level (AHL) » Topic 18: Acids and bases » 18.2 Calculations involving acids and bases

Additional higher level (AHL) » Topic 18: Acids and bases

Core » Topic 8: Acids and bases » 8.1 Theories of acids and bases

Core » Topic 8: Acids and bases

Question 20N.2.hl.TZ0.5d

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