DP Chemistry (last assessment 2024)
Question 19M.2.hl.TZ1.3g(i)
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.2.hl.TZ1.3g(i) |
| Level | hl | Paper | 2 | Time zone | TZ1 |
| Command term | Determine | Question number | g(i) | Adapted from | N/A |
g(i).
[Maximum mark: 3]
19M.2.hl.TZ1.3g(i)
This question is about sodium and its compounds.
Sodium peroxide is used in diving apparatus to produce oxygen from carbon dioxide.
2Na2O2 (s) + 2CO2 (g) → 2Na2CO3 (s) + O2 (g)
(g(i))
Determine the enthalpy change, ΔH, in kJ, for this reaction using data from the table and section 12 of the data booklet.
[3]
Markscheme
∑ΔHf products = 2 × (−1130.7) / −2261.4 «kJ» [✔]
∑ΔHf reactants = 2 × (−510.9) + 2 × (−393.5) / −1808.8 «kJ» [✔]
ΔH = «∑ΔHf products − ∑ΔHf reactants = −2261.4 −(−1808.8) =» −452.6 «kJ» [✔]
Note: Award [3] for correct final answer.
Award [2 max] for “+ 452.6 «kJ»”.
Examiners report
The average was 2.2 out 3 for this question on enthalpy of formation. Enthalpy calculations were generally well done.
