DP Chemistry (last assessment 2024)
Question 17N.3.hl.TZ0.14
| Date | November 2017 | Marks available | [Maximum mark: 2] | Reference code | 17N.3.hl.TZ0.14 |
| Level | hl | Paper | 3 | Time zone | TZ0 |
| Command term | Outline, State | Question number | 14 | Adapted from | N/A |
14.
[Maximum mark: 2]
17N.3.hl.TZ0.14
The heme groups in cytochromes contain iron ions that are involved in the reduction of molecular oxygen.
(a)
State the half-equation for the reduction of molecular oxygen to water in acidic conditions.
[1]
Markscheme
O2 + 4H+ (aq) + 4e– → 2H2O (l)
Accept any balanced equation with any integer or fractional coefficients.
(b)
Outline the change in oxidation state of the iron ions in heme groups that occurs when molecular oxygen is converted to water.
[1]
Markscheme
+2 to +3
OR
+1
OR
increases «by 1»