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Date May 2019 Marks available 1 Reference code 19M.1.sl.TZ1.19
Level SL Paper 1 Time zone TZ1
Command term Question number 19 Adapted from N/A

Question

Which solution is basic at 25 °C?

Kw = 1.0 × 10−14

A. [H+] = 1.0 × 10−3 mol dm−3

B. [OH] = 1.0 × 10−13 mol dm−3

C. solution of pH = 4.00

D. [H3O+] = 1.0 × 10−13 mol dm−3

Markscheme

D

Examiners report

This was very poorly answered and had one of the highest discriminatory indices. More candidates thought that a basic solution would have [OH- ] = 1.0 x 10-13 mol dm-3 , rather than [H3O+ ] = 1.0 x 10-13 mol dm-3

Syllabus sections

Core » Topic 8: Acids and bases » 8.3 The pH scale
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Core » Topic 8: Acids and bases
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