DP Chemistry (last assessment 2024)
Question 19M.2.sl.TZ1.a(ii)
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.2.sl.TZ1.a(ii) |
| Level | sl | Paper | 2 | Time zone | TZ1 |
| Command term | Write | Question number | a(ii) | Adapted from | N/A |
a(ii).
[Maximum mark: 3]
19M.2.sl.TZ1.a(ii)
This question is about compounds of sodium.
Write equations for the separate reactions of solid sodium oxide and solid phosphorus(V) oxide with excess water and differentiate between the solutions formed.
Sodium oxide, Na2O:
Phosphorus(V) oxide, P4O10:
Differentiation:
[3]
Markscheme
Sodium oxide:
Na2O(s) + H2O(l) → 2NaOH (aq) [✔]
Phosphorus(V) oxide:
P4O10 (s) + 6H2O(l) → 4H3PO4 (aq) [✔]
Differentiation:
NaOH / product of Na2O is alkaline/basic/pH > 7 AND H3PO4 / product of P4O10 is acidic/pH < 7 [✔]
Examiners report
Very few students could correctly write out the two equations and so often were unable to realise it was acid/base behaviour that would differentiate the oxides.
