DP Chemistry (first assessment 2025)
Question 22N.1A.SL.TZ0.19
| Date | November 2022 | Marks available | [Maximum mark: 1] | Reference code | 22N.1A.SL.TZ0.19 |
| Level | SL | Paper | 1A | Time zone | TZ0 |
| Command term | State | Question number | 19 | Adapted from | N/A |
19.
[Maximum mark: 1]
22N.1A.SL.TZ0.19
Equal volumes of 0.10 mol dm−3 weak acid and strong acid are titrated with 0.10 mol dm−3 NaOH solution. Which of these is the same for the two acids?
A. Initial pH
B. Heat evolved in the neutralization
C. Volume of NaOH for complete neutralization
D. Initial electrical conductivity
[1]
Markscheme
C
Examiners report
48% of the candidates deduced that the volume of NaOH required to neutralize the strong and weak acid samples would be the same. The most commonly chosen distractor was that the heat evolved would be the same. Surprisingly this question did not discriminate very well between high-scoring and low-scoring candidates. Some teachers commented that the question should have specified that the acids were monoprotic.
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.
Reactivity 2. How much, how fast and how far? » Reactivity 2.2—How fast? The rate of chemical change » Reactivity 2.2.3—Factors that influence the rate of a reaction include pressure, concentration, surface area, temperature and the presence of a catalyst. Predict and explain the effects of changing conditions on the rate of a reaction.