DP Chemistry (first assessment 2025)
Question 19M.2.HL.TZ2.e(iii)
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.2.HL.TZ2.e(iii) |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Predict | Question number | e(iii) | Adapted from | N/A |
e(iii).
[Maximum mark: 1]
19M.2.HL.TZ2.e(iii)
Predict, giving a reason, whether the reduction of ReO4− to [Re(OH)2]2+ would oxidize Fe2+ to Fe3+ in aqueous solution. Use section 24 of the data booklet.
[1]
Markscheme
no AND ReO4− is a weaker oxidizing agent than Fe3+
OR
no AND Fe3+ is a stronger oxidizing agent than ReO4−
OR
no AND Fe2+ is a weaker reducing agent than [Re(OH)2]2+
OR
no AND [Re(OH)2]2+ is a stronger reducing agent than Fe2+
OR
no AND cell emf would be negative/–0.41 V [✔]
Examiners report
Many students understood that the oxidation of Fe2+ was not viable but were unable to explain why in terms of oxidizing and reducing power; many students simply gave numerical values for EΘ often failing to realise that the oxidation of Fe2+ would have the inverse sign to the reduction reaction.
Syllabus sections
Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.2—Electron transfer reactions » Reactivity 3.2.13—Standard cell potential, E⦵cell, can be calculated from standard electrode potentials. E⦵cell has a positive value for a spontaneous reaction. Predict whether a reaction is spontaneous in the forward or reverse direction from E⦵ data.