DP Chemistry (last assessment 2024)

Test builder »

Question 21N.2.hl.TZ0.a

Select a Test
Date November 2021 Marks available [Maximum mark: 2] Reference code 21N.2.hl.TZ0.a
Level hl Paper 2 Time zone TZ0
Command term Calculate Question number a Adapted from N/A
a.
[Maximum mark: 2]
21N.2.hl.TZ0.a

50.00 cm3 of 0.75 mol dm−3 sodium hydroxide was added in 1.00 cm3 portions to 22.50 cm3 of 0.50 mol dm−3 chloroethanoic acid.

Calculate the initial pH before any sodium hydroxide was added, using section 21 of the data booklet.

[2]

Markscheme

«Ka = 10–2.87 = 1.35 × 10–3 »

«1.35 × 10–3 = chloroethanoate×H+0.50 mol dm-3=x20.50 mol dm-3 »

«x = [H+] =1.4×10-3×0.50=» 2.6 × 10–2 «mol dm–3» ✔


«pH = –log[H+] = –log(2.6 × 10–2) =» 1.59 ✔

 

Accept final answer in range 1.58–1.60.

Award [2] for correct final answer.

Syllabus sections