DP Chemistry (last assessment 2024)
Question 21M.2.hl.TZ1.4e(i)
| Date | May 2021 | Marks available | [Maximum mark: 2] | Reference code | 21M.2.hl.TZ1.4e(i) |
| Level | hl | Paper | 2 | Time zone | TZ1 |
| Command term | Calculate | Question number | e(i) | Adapted from | N/A |
e(i).
[Maximum mark: 2]
21M.2.hl.TZ1.4e(i)
Hydrogen peroxide can react with methane and oxygen to form methanol. This reaction can occur below 50°C if a gold nanoparticle catalyst is used.
Now consider the second stage of the reaction.
CO (g) + 2H2 (g) CH3OH (l) ΔH⦵ = –129 kJ
(e(i))
The equilibrium constant, Kc, has a value of 1.01 at 298 K.
Calculate ΔG⦵, in kJ mol–1, for this reaction. Use sections 1 and 2 of the data booklet.
[2]
Markscheme
«ΔG⦵ = − RT lnKc»
ΔG⦵ = − 8.31 «J K−1 mol−1» × 298 «K» × ln (1.01) / −24.6 «J mol−1» ✔
= −0.0246 «kJ mol–1» ✔
Award [2] for correct final answer.
Award [1 max] for +0.0246 «kJ mol–1».
