DP Chemistry (last assessment 2024)

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Question 20N.2.hl.TZ0.5b(i)

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Date November 2020 Marks available [Maximum mark: 2] Reference code 20N.2.hl.TZ0.5b(i)
Level hl Paper 2 Time zone TZ0
Command term Identify Question number b(i) Adapted from N/A
b(i).
[Maximum mark: 2]
20N.2.hl.TZ0.5b(i)

A student performs a titration to determine the concentration of ethanoic acid, CH3COOH, in vinegar using potassium hydroxide.

The pH curve for the reaction is given.

(b(i))

Identify the major species, other than water and potassium ions, at these points.

[2]

Markscheme

B: CH3COOH  AND CH3COO− ✔

C: CH3COO− ✔

Accept names.

Accept CH3COOK for CH3COO−

Examiners report

Identifying species present at various points along a pH titration curve was one of the most poorly answered questions in the exam. Very few candidates realized there were two major species at point B even when they were able in general to realize that B was a buffer zone.

Syllabus sections