DP Chemistry (first assessment 2025)
Question 22N.1A.HL.TZ0.27
| Date | November 2022 | Marks available | [Maximum mark: 1] | Reference code | 22N.1A.HL.TZ0.27 |
| Level | HL | Paper | 1A | Time zone | TZ0 |
| Command term | Apply | Question number | 27 | Adapted from | N/A |
27.
[Maximum mark: 1]
22N.1A.HL.TZ0.27
Which species can act both as a Lewis acid and a Lewis base?
A. H2O
B. NH4+
C. Cu2+
D. CH4
[1]
Markscheme
A
Examiners report
Nearly 65% of candidates correctly identified water as being able to act as both a Lewis acid and a Lewis base. Cu2+ (C) was the most favoured of the distractors and gaining this mark seemed to be only weakly related to overall performance.
Syllabus sections
Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.4—Electron-pair sharing reactions » Reactivity 3.4.6—A Lewis acid is an electron-pair acceptor and a Lewis base is an electron-pair donor. Apply Lewis acid–base theory to inorganic and organic chemistry to identify the role of the reacting species.