Potentiometry is to be used to determine the concentration of ametal dication, M2+,
in water. The table below shows the dependence of the cellpotential on [M2+]
(please note some data has been deliberately omitted).
| [M2+] / mol l-1 | ECell / V |
| 1 | |
| 0.5 | -0.295 |
| 0.1 | -0.309 |
| 0.05 | -0.325 |
| 0.025 | |
| 0.01 | -0.349 |
| 0.005 | -0.354 |
Q 2(a)
With the aid of a graph, determine the Nernst slope and theStandard Cell Potential,
Eo’. Comment on the values obtained and state the number ofelectrons transferred.
Q 2(b)
Clearly explaining your reasoning, use the graph to estimate thepotentials that are
missing in the table. Comment on the likely accuracy of yourpredictions.
Q 2(c)
The Standard Cell Potential for Cd2+/Cd is -0.43V, for Pb2+/Pb is-0.29 V and for
Cu2+/Cu is +0.34 V. Clearly explaining your reasoning, determinethe likely identity
of the metal cation.
Q 2(d)
If the potential measured for an unknown solution is -0.318 V,determine the
concentration of M2+ in the sample.
