The E°cell is positive in the direction stated, therefore the reaction is spontaneous in the direction calculated (i.e. reduction in the Cu half cell and oxidation in the Ni half cell). As this spontaneous reaction occurs, the chemical potential energy is converted into electrical energy as seen in the positive voltage (can be used e.g. in a battery) Cell 7 Assume the Al half cell is oxidation and the Pb is reduction E°cell = E°(R) - E°(O), =-0.13 -1.66 = 1.53V positive Ecell means this is the correct direction. – – Reduction: Pb2++ 2e Pb (reduction as ON of Pb is decreasing from +2 in Pb2+ to 0 in Pb, decrease in ON = → reduction) Oxidation: Al + 3e Al3+ (oxidation as ON of Al is increasing from to 0 in Al to +3 in Al+3, increase in ON = → oxidation) Overall: 2Al + 3Pb 2Al3++ 3Pb2+ → Observations LHC: Colourless Al3+ is produced from Al at the anode. The colour of the solution will not change, but the electrode would decrease in mass as a grey solid (Al) oxidised. RHC: The electrode would increase in mass as the grey solid Pb is produced by reduction of the colourless solution Pb2+. The colour of the solution would not change. The E°cell is positive, therefore the reaction is spontaneous in the direction calculated (i.e. reduction in the Pb half cell and oxidation in the Al half cell). As this spontaneous reaction occurs, the chemical potential energy is converted into electrical energy as seen in the positive voltage (can be used e.g. in a battery) Cell 8
The E°cell is positive in the direction stated, therefore the reaction is spontaneous in the direction calculated (i.e. reduction in the Cu half cell and oxidation in the Ni half cell). As this spontaneous reaction occurs, the chemical potential energy is converted into electrical energy as seen in the positive voltage (can be used e.g. in a battery) Cell 7 Assume the Al half cell is oxidation and the Pb is reduction E°cell = E°(R) - E°(O), =-0.13 – -1.66 = 1.53V – positive Ecell means this is the correct direction. Reduction: Pb2++ 2e → Pb (reduction as ON of Pb is decreasing from +2 in Pb2+ to 0 in Pb, decrease in ON = reduction) Oxidation: Al + 3e → Al3+ (oxidation as ON of Al is increasing from to 0 in Al to +3 in Al+3, increase in ON = oxidation) Overall: 2Al + 3Pb → 2Al3++ 3Pb2+ Observations LHC: Colourless Al3+ is produced from Al at the anode. The colour of the solution will not change, but the electrode would decrease in mass as a grey solid (Al) oxidised. RHC: The electrode would increase in mass as the grey solid Pb is produced by reduction of the colourless solution Pb2+. The colour of the solution would not change. The E°cell is positive, therefore the reaction is spontaneous in the direction calculated (i.e. reduction in the Pb half cell and oxidation in the Al half cell). As this spontaneous reaction occurs, the chemical potential energy is converted into electrical energy as seen in the positive voltage (can be used e.g. in a battery) Cell 8
answers_analysing_electrochemical_cells.docx