DP Chemistry (first assessment 2025)
Question 19M.2.SL.TZ2.e(ii)
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.2.SL.TZ2.e(ii) |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Deduce | Question number | e(ii) | Adapted from | N/A |
e(ii).
[Maximum mark: 1]
19M.2.SL.TZ2.e(ii)
Deduce the coefficients required to complete the half-equation.
ReO4− (aq) + ____H+ (aq) + ____e− ⇌ [Re(OH)2]2+ (aq) + ____H2O (l) Eθ = +0.36 V
[1]
Markscheme
ReO4− (aq) + 6H+ (aq) + 3e− ⇌ [Re(OH)2]2+ (aq) + 2H2O (l) [✔]
Examiners report
Surprisingly, a great number of students were unable to balance this simple half-equation that was given to them to avoid difficulties in recall of reactants/products.
Syllabus sections
Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.2—Electron transfer reactions » Reactivity 3.2.2—Half-equations separate the processes of oxidation and reduction, showing the loss or gain of electrons. Deduce redox half-equations and equations in acidic or neutral solutions.