DP Chemistry (first assessment 2025)

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Question 20N.1A.SL.TZ0.20

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

20.

[Maximum mark: 1]

20N.1A.SL.TZ0.20

Which of these acids has the weakest conjugate base?

A. $HCl$

B. ${CH}_{3} COOH$

C. ${NH}_{4} Cl$

D. $C_{6} H_{5} COOH$

[1]

Markscheme

A

Examiners report

More than 59% of the candidates understood that strong acids have weak conjugate bases.

Syllabus sections

Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.1—Proton transfer reactions » Reactivity 3.1.6—Strong and weak acids and bases differ in the extent of ionization. Recognize that acid–base equilibria lie in the direction of the weaker conjugate. and are strong acids, and group 1 hydroxides are strong bases.