DP Chemistry (first assessment 2025)
Question 22M.1A.HL.TZ2.26
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.1A.HL.TZ2.26 |
| Level | HL | Paper | 1A | Time zone | TZ2 |
| Command term | Estimate | Question number | 26 | Adapted from | N/A |
26.
[Maximum mark: 1]
22M.1A.HL.TZ2.26
A weak base is titrated with a strong acid. Which value of pKb can be estimated from this titration curve?
A. 11.3
B. 9.2
C. 4.8
D. 1.8
[1]
Markscheme
C
Examiners report
Only 29% of candidates determined pKb from the titration curve. The majority of the candidates made the mistake of using the pH without calculating the corresponding pOH.
Syllabus sections
Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.1—Proton transfer reactions » Reactivity 3.1.13—pH curves of different combinations of strong and weak monoprotic acids and bases have characteristic shapes and features. Interpret the general shapes of pH curves for all four combinations of strong and weak acids and bases.