The photosynthesis equation is given as: $\text{6CO}_2 + \text{6H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + \text{6O}_2$. In this process, water undergoes oxidation according to the half-equation: $\text{2H}_2\text{O} \rightarrow \text{O}_2 + \text{4H}^+ + \text{4e}^-$ (half-equation 1).
(a(i))[2]
Use these equations to work out the half-equation for the reduction of carbon dioxide in this process.
(a(ii))[4]
Draw a fully labelled diagram of the apparatus needed to measure the standard electrode potential, $E^{\circ}$, of $\text{O}_2(g)$ in half-equation 1 under standard conditions. Include all necessary chemicals.
(a(iii))[1]
For the cell drawn in (a)(ii), use the Data Booklet to calculate $E^{\circ}_{\text{cell}}$ and deduce which electrode is positive.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Accepted form: $6CO_2 + 24H^+ + 24e^- \rightarrow C_6H_{12}O_6 + 6H_2O$ (or a valid alternative).” …