DP Chemistry (last assessment 2024)
Question 19M.2.hl.TZ2.2g(i)
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.hl.TZ2.2g(i) |
| Level | hl | Paper | 2 | Time zone | TZ2 |
| Command term | Determine | Question number | g(i) | Adapted from | N/A |
g(i).
[Maximum mark: 2]
19M.2.hl.TZ2.2g(i)
The thermal decomposition of dinitrogen monoxide occurs according to the equation:
2N2O (g) → 2N2 (g) + O2 (g)
The reaction can be followed by measuring the change in total pressure, at constant temperature, with time.
The x-axis and y-axis are shown with arbitrary units.
(g(i))
Determine the standard entropy change, in J K−1, for the decomposition of dinitrogen monoxide.
2N2O (g) → 2N2 (g) + O2 (g)
[2]
Markscheme
ΔSθ = 2(Sθ(N2)) + Sθ(O2) – 2(Sθ(N2O))
OR
ΔSθ = 2 × 193 «J mol-1 K-1» + 205 «J mol-1 K-1» – 2 × 220 «J mol-1 K-1» [✔]
«ΔSθ = +»151 «J K-1» [✔]
Note: Award [2] for correct final answer.
Examiners report
Candidates were able to calculate the ΔS of the reaction, though in some cases they failed to multiply by the number of moles.
