Chemistry 9701 · AS & A Level · Electrochemistry

Electrochemistry — practice question

(a(i))[3]

Identify what $A$ to $F$ stand for.

(a(ii))[1]

Label the diagram to indicate the positive electrode and the direction of electron flow in the external circuit.

(b)[1]

In a different experiment, an $\text{Fe}^{3+}(aq)/\text{Fe}^{2+}(aq)$ half-cell was connected to a $\text{Cu}^{2+}(aq)/\text{Cu}(s)$ half-cell. Determine the standard cell potential, $E^\circ_{\text{cell}}$, when these two half-cells are joined by a wire and the circuit is completed.

(c(i))[1]

The $E^\circ$ of $\text{Ni}^{2+}(aq)/\text{Ni}(s)$ is $-0.25\,\text{V}$. State and explain how the electrode potential changes when the concentration of $\text{Ni}^{2+}(aq)$ is reduced.

(c(ii))[2]

The $E^\circ$ of $\text{Cr}^{3+}(aq)/\text{Cr}^{2+}(aq)$ is $-0.41\,\text{V}$. Calculate the electrode potential when $[\text{Cr}^{3+}(aq)]$ is $0.60\,\text{mol dm}^{-3}$ and $[\text{Cr}^{2+}(aq)]$ is $0.15\,\text{mol dm}^{-3}$. Use the Nernst equation. $E = E^\circ + \frac{0.059}{z} \log\left(\frac{[\text{oxidised species}]}{[\text{reduced species}]}\right)$

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: Accurate identification of the cell parts, including $\mathrm{H_2}$ at $1\ \mathrm{atm}$, Pt electrodes, the salt bridge and the correct concentrations

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