DP Chemistry (last assessment 2024)

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Question 21M.2.hl.TZ1.8a

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Date May 2021 Marks available [Maximum mark: 3] Reference code 21M.2.hl.TZ1.8a
Level hl Paper 2 Time zone TZ1
Command term Calculate Question number a Adapted from N/A
a.
[Maximum mark: 3]
21M.2.hl.TZ1.8a

Propanoic acid, CH3CH2COOH, is a weak organic acid.

(a)

Calculate the pH of 0.00100 mol dm–3 propanoic acid solution. Use section 21 of the data booklet.

[3]

Markscheme

Ka = 10−4.87 / 1.35 × 10−5 ✔

[H+] = «1.35×10-5×0.001=1.35×10-8=» 1.16 × 10−4 «mol dm−3» ✔

pH = 3.94 ✔


Accept alternative methods of calculation.

Award [3] for correct final answer.

Award [3] for 3.96 {answer if solved by quadratic}.

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