DP Chemistry (last assessment 2024)
Question 17N.3.hl.TZ0.20a
| Date | November 2017 | Marks available | [Maximum mark: 3] | Reference code | 17N.3.hl.TZ0.20a |
| Level | hl | Paper | 3 | Time zone | TZ0 |
| Command term | Deduce | Question number | a | Adapted from | N/A |
a.
[Maximum mark: 3]
17N.3.hl.TZ0.20a
A fuel cell converts chemical energy directly to electrical energy.
(a)
Deduce the half-equations and the overall equation for the reactions taking place in a direct methanol fuel cell (DMFC) under acidic conditions.
[3]
Markscheme
Negative electrode (anode):
CH3OH (aq) + H2O (l) → CO2 (g) + 6H+ (aq) + 6e–
Positive electrode (cathode):
O2 (g) + 4H+ (aq) + 4e– → 2H2O (l)
Overall equation:
2CH3OH (aq) + 3O2 (g) → 2CO2 (g) + 4H2O (l)
Accept any whole or fractional coefficients in balanced equations.
Award [1 max] for correct half-equations at wrong electrodes for M1 and M2.