DP Chemistry (first assessment 2025)
Question 22N.1A.SL.TZ0.20
| Date | November 2022 | Marks available | [Maximum mark: 1] | Reference code | 22N.1A.SL.TZ0.20 |
| Level | SL | Paper | 1A | Time zone | TZ0 |
| Command term | Deduce | Question number | 20 | Adapted from | N/A |
20.
[Maximum mark: 1]
22N.1A.SL.TZ0.20
Which species has the weakest conjugate base?
A. HCl
B. NH4+
C. HCO3−
D. H2O
[1]
Markscheme
A
Examiners report
48% of the candidates chose HCl as the species with the weakest conjugate base. This question had good discrimination between high-scoring and low-scoring candidates.
Syllabus sections
Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.1—Proton transfer reactions » Reactivity 3.1.6—Strong and weak acids and bases differ in the extent of ionization. Recognize that acid–base equilibria lie in the direction of the weaker conjugate. and are strong acids, and group 1 hydroxides are strong bases.