The photosynthesis overall equation is given as: $6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$. In this process, water is oxidised according to the half-equation below: $2\text{H}_2\text{O} \rightarrow \text{O}_2 + 4\text{H}^+ + 4e^-.$
(a(i))[2]
Use these equations to deduce the half-equation for the reduction of carbon dioxide in this process.
(a(ii))[4]
Provide a fully labelled diagram of the apparatus used to measure the standard electrode potential, $E^\circ$, of 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 determine 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: “$6CO_2 + 24H^+ + 24e^- \rightarrow C_6H_{12}O_6 + 6H_2O$ (or an equivalently balanced equation)” …