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15 exam-style questions with model answers, plus 20 quick multi-choice questions — every question on the site for this standard, grouped by the 5 pages of notes they come from.
Write a full answer before you reveal the model one — that comparison is where the marks come from. Every block links back to the notes that teach it.
State the standard conditions for a reduction potential, explain why the standard hydrogen electrode is assigned a value of 0.00 V, and state what a more positive E° indicates.
Explain why the E° value is unchanged when a half equation is multiplied through, using the silver half equation as an example.
Compare and contrast what the reduction potential table tells you with what the reactivity series tells you, and justify why the table is the more powerful tool.
Calculate E°cell for the reaction between zinc metal and silver ions, and state whether it is spontaneous. (E° Ag+/Ag = +0.80 V; E° Zn2+/Zn = −0.76 V)
Explain, with a calculation, why acidified potassium permanganate oxidises chloride ions but acidified potassium dichromate does not, and state the observations in each case. (E° MnO4−/Mn2+ = +1.51 V; E° Cr2O72−/Cr3+ = +1.33 V; E° Cl2/Cl− = +1.36 V)
Aluminium has E° = −1.66 V for Al3+/Al, and water has E° = −0.83 V for the reduction of water to hydrogen. This predicts aluminium should react vigorously with water, yet aluminium saucepans are stable. Justify why the prediction fails, and evaluate what this reveals about the limitations of E° as a predictive tool.
For a magnesium–copper galvanic cell, identify the anode and cathode, state which species is oxidised and which reduced, and calculate E°cell. (E° Mg2+/Mg = −2.37 V; E° Cu2+/Cu = +0.34 V)
Explain why a salt bridge is necessary in a galvanic cell, describing what happens without one and which way the ions move.
A student measures 1.05 V from a nickel–silver cell initially, but after several hours the reading has fallen to 0.92 V, and the cell eventually stops. Justify why the voltage falls, and compare this behaviour with what would happen if the same reaction were carried out by simply adding nickel powder to silver nitrate solution.
For the electrolysis of molten magnesium chloride, write the half equation at each electrode, state the sign of each electrode, and state what would be observed.
Explain why sodium metal is produced when molten sodium chloride is electrolysed, but hydrogen is produced when aqueous sodium chloride is electrolysed. Use E° values in your answer.
In the electrolysis of concentrated brine, E° values predict that water should be oxidised at the anode in preference to chloride, yet chlorine gas is the observed product. Justify why the prediction fails, and evaluate what this shows about using E° to predict electrolysis products.
State three ways in which an electrochemical cell and an electrolytic cell differ, and two ways in which they are the same.
Explain why the anode is negative in an electrochemical cell but positive in an electrolytic cell, even though oxidation occurs at the anode in both.
Compare and contrast the oxidation–reduction processes in a lead–acid car battery when it is discharging and when it is being charged. Justify your answer with half equations, and evaluate what this example shows about the relationship between the two cell types.