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