A student was asked to perform a first-hand investigation to measure the difference in potential of various combinations of metals in an electrolyte solution - HSC - SSCE Chemistry - Question 19 - 2006 - Paper 1

To set up the experiment, draw a simple diagram with two half-cells: one containing aluminium in aluminium nitrate solution, and the other containing silver in silver nitrate solution. Label the electrodes, the connecting wire, and the voltmeter that measures the potential difference between the two electrodes.

The balanced chemical reaction between aluminium and silver can be represented as:

$ext{2Al} + ext{3Ag}^+ \rightarrow \text{2Al}^{3+} + \text{3Ag}$

The standard electrode potential for aluminium is approximately -1.66 V and for silver is +0.80 V. The expected potential difference can be calculated as:

$E_{cell} = E_{Ag^+/Ag} - E_{Al^{3+/Al}} = 0.80 - (-1.66) = 2.46 V$

To minimize the variation between the measured and theoretical potential difference, the student could take the following steps:

1. Ensure that the electrodes are cleaned properly before each measurement to remove any contaminants that may affect the results.
2. Use fresh electrolyte solutions to avoid issues with concentration changes over time.
3. Maintain consistent temperature conditions during the experiment as temperature can affect electrode potentials.
4. Ensure proper calibration and functionality of the voltage measuring device, such as a voltmeter, before starting the experiments.