Question 19M.2.sl.TZ1.c(i)
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.2.sl.TZ1.c(i) |
| Level | sl | Paper | 2 | Time zone | TZ1 |
| Command term | Determine | Question number | c(i) | Adapted from | N/A |
This question is about compounds of sodium.
Sodium peroxide is used in diving apparatus to produce oxygen from carbon dioxide.
2Na2O2 (s) + 2CO2 (g) → 2Na2CO3 (s) + O2 (g)
Determine the enthalpy change, ΔH, in kJ, for this reaction using data from the table and section 12 of the data booklet.
[3]
ΣΔHf products = 2 × (−1130.7) / −2261.4 «kJ» [✔]
ΣΔHf reactants = 2 × (−510.9) + 2 × (−393.5) / −1808.8 «kJ» [✔]
ΔH = «ΣΔHf products − ΣΔHf reactants = −2261.4 −(−1808.8) =» −452.6 «kJ» [✔]
Note: Award [3] for correct final answer.
Award [2 max] for “+452.6 «kJ»”.
The calculation of the enthalpy change using enthalpies of formation was generally answered well but common mistakes were students forgetting to multiply by 2 or adding extra terms for oxygen.
