DP Chemistry (last assessment 2024)
Question 21N.2.hl.TZ0.b
| Date | November 2021 | Marks available | [Maximum mark: 2] | Reference code | 21N.2.hl.TZ0.b |
| Level | hl | Paper | 2 | Time zone | TZ0 |
| Command term | Formulate | Question number | b | Adapted from | N/A |
b.
[Maximum mark: 2]
21N.2.hl.TZ0.b
Phosphoric acid, H3PO4 can form three different salts depending on the extent of neutralisation by sodium hydroxide.
Formulate two equations to show the amphiprotic nature of H2PO4−.
[2]
Markscheme
H2PO4− (aq) + H+ (aq) → H3PO4 (aq) ✔
H2PO4− (aq) + OH− (aq) → HPO42− (aq) + H2O (l) ✔
Accept reactions of H2PO4− with any acidic, basic or amphiprotic species, such as H3O+, NH3 or H2O.
Accept H2PO4− (aq) → HPO42− (aq) + H+ (aq) for M2.
