Write the balanced equation for the reaction in this voltaic cell.

Calculate the cell potential for $0.0100 \mathrm{mol} {\mathrm{dm}}^{-3} {\mathrm{Mg}}^{2+}\left(\mathrm{aq}\right)$ and $0.800 \mathrm{mol} {\mathrm{dm}}^{-3} {\mathrm{Ni}}^{2+}\left(\mathrm{aq}\right)$ at $298 \mathrm{K}$. Use sections 1, 2 and 24 of the data booklet.

Predict, giving a reason, how an increase in temperature affects the potential of this cell.

The Geobacter species of bacteria can be used in microbial fuel cells to oxidise aqueous ethanoate ions,
CH₃COO⁻(aq), to carbon dioxide gas.

State the half-equations for the reactions at both electrodes.

A concentration cell is an example of an electrochemical cell.

(i) State the difference between a concentration cell and a standard voltaic cell.

(ii) The overall redox equation and the standard cell potential for a voltaic cell are:

Zn (s) + Cu²⁺ (aq) → Zn²⁺ (aq) + Cu (s)     E^θ_cell = +1.10 V

Determine the cell potential E at 298 K to three significant figures given the following concentrations in mol dm⁻³:

[Zn²⁺] = 1.00 × 10⁻⁴       [Cu²⁺] = 1.00 × 10⁻¹

Use sections 1 and 2 of the data booklet.

(iii) Deduce, giving your reason, whether the reaction in (b) (ii) is more or less spontaneous than in the standard cell.

Dye-sensitized solar cells (DSSC) convert solar energy into electrical energy.

(i) Describe how a DSSC converts sunlight into electrical energy.

(ii) Explain the role of the electrolyte solution containing iodide ions, I⁻, and triiodide ions, I₃⁻, in the DSSC.

Deduce the half-equations for the reactions occurring at the electrodes.

Anode (negative electrode):

Cathode (positive electrode):

Calculate the cell potential, E^θ, in V, using section 24 of the data booklet.

Suggest how PEM fuel cells can be used to produce a larger voltage than that calculated in (b)(i).

Suggest an advantage of the PEM fuel cell over the lead-acid battery for use in cars.

Outline the functions of the dye, TiO₂ and the electrolyte in the operation of the DSSC.

Dye: 

TiO₂:

Electrolyte:

Suggest an advantage of the DSSC over silicon-based photovoltaic cells.