DP Chemistry (first assessment 2025)
Question 22N.1A.HL.TZ0.26
| Date | November 2022 | Marks available | [Maximum mark: 1] | Reference code | 22N.1A.HL.TZ0.26 |
| Level | HL | Paper | 1A | Time zone | TZ0 |
| Command term | Identify | Question number | 26 | Adapted from | N/A |
26.
[Maximum mark: 1]
22N.1A.HL.TZ0.26
Which solutions will form a buffer when mixed?
A. 50 cm3 of 1.0 mol dm−3 HCl and 50 cm3 of 1.0 mol dm−3 NaOH
B. 50 cm3 of 1.0 mol dm−3 CH3COOH and 50 cm3 of 1.0 mol dm−3 NaOH
C. 50 cm3 of 1.0 mol dm−3 CH3COOH and 100 cm3 of 1.0 mol dm−3 NaOH
D. 100 cm3 of 1.0 mol dm−3 CH3COOH and 50 cm3 of 1.0 mol dm−3 NaOH
[1]
Markscheme
D
Examiners report
Over 70% of candidates answered correctly, realising that partial neutralization of a weak acid by a strong base produces a buffer solution and there was quite a strong link with overall performance. Complete neutralization to give the salt (B) was the most frequently chosen distractor.
Syllabus sections
Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.1—Proton transfer reactions » Reactivity 3.1.16—A buffer solution is one that resists change in pH on the addition of small amounts of acid or alkali. Describe the composition of acidic and basic buffers and explain their actions.