DP Chemistry (first assessment 2025)

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Question 21M.1A.HL.TZ1.27

Date	May 2021	Marks available	[Maximum mark: 1]	Reference code	21M.1A.HL.TZ1.27
Level	HL	Paper	1A	Time zone	TZ1
Command term	Identify	Question number	27	Adapted from	N/A

27.

[Maximum mark: 1]

21M.1A.HL.TZ1.27

Which combination will produce an alkaline buffer in water?

A. 0.10 mol NH₃ and 0.05 mol H₂SO₄

B. 0.50 mol NH₃ and 0.10 mol H₂SO₄

C. 0.10 mol CH₃COOH and 0.05 mol NaOH

D. 0.10 mol CH₃COOH and 0.50 mol NaOH

[1]

Markscheme

B

Syllabus sections

Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.1—Proton transfer reactions » Reactivity 3.1.17—The pH of a buffer solution depends on both: • the pKa or pKb of its acid or base • the ratio of the concentration of acid or base to the concentration of the conjugate base or acid. Solve problems involving the composition and pH of a buffer solution, using the equilibrium constant.