DP Chemistry (last assessment 2024)
Question 19M.3.hl.TZ2.a(ii)
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.3.hl.TZ2.a(ii) |
| Level | hl | Paper | 3 | Time zone | TZ2 |
| Command term | Calculate | Question number | a(ii) | Adapted from | N/A |
a(ii).
[Maximum mark: 1]
19M.3.hl.TZ2.a(ii)
Amino acids contain both acidic and basic functional groups.
An aqueous solution of glutamine contains 0.600 mol dm−3 of the zwitterion and 0.300 mol dm−3 of the anionic form.
pKa1 = 2.2 and pKa2 = 9.1
Calculate the pH of the glutamine solution using section 1 of the data booklet.
[1]
Markscheme
«pH = 9.1 + log »
«= 9.1 + (–0.3)» = 8.8 [✔]
Examiners report
Majority of the candidates calculated correctly the pH of the glutamine solution while other candidates managed the ECF mark from part a (i).
