Quick answer: Electrochemistry links redox reactions to electrical energy. This AP Chemistry test on electrochemistry has 8 questions worth 20 marks, to do in 40 minutes: anode and cathode, magnesium and nickel cell and free energy and K for tin and copper. The mark scheme is on a separate page; free printable PDF.
This test covers cell potentials, free energy, equilibrium, the Nernst equation and Faraday’s law. Show all working and give units. A data table is allowed. The paper is worth 20 marks.
Level: AP Chemistry · Curriculum: AP Chem Unit 9
Question 1 Anode and cathode (2 marks)
- State the process that occurs at the anode of any cell. (1 mark)
- State the sign of the anode in a galvanic cell and in an electrolytic cell. (1 mark)
Question 2 Magnesium and nickel cell (3 marks)
E°(Mg²⁺/Mg) = −2.37 V; E°(Ni²⁺/Ni) = −0.25 V. A cell is built from these half-cells.- Identify the cathode and write its half-reaction. (1 mark)
- Calculate E°cell. (1 mark)
- Write the balanced overall equation. (1 mark)
Question 3 Free energy and K for tin and copper (3 marks)
Sn + Cu²⁺ → Sn²⁺ + Cu. E°(Cu²⁺/Cu) = +0.34 V, E°(Sn²⁺/Sn) = −0.14 V. Use F = 96 485 C/mol and log K = nE°/0.0592.- Calculate E°cell. (1 mark)
- Calculate ΔG° in kJ/mol. (1 mark)
- Calculate K. (1 mark)
Question 4 Voltage away from standard (2 marks)
A Zn/Cu cell has [Zn²⁺] = 0.010 mol/dm³ and [Cu²⁺] = 1.0 mol/dm³ at 25 °C. E° = 1.10 V and n = 2.- Calculate Q. (1 mark)
- Calculate E using the Nernst equation. (1 mark)
Question 5 Silver plating (3 marks)
A current of 0.500 A flows for 30.0 min through silver nitrate solution, Ag⁺ + e⁻ → Ag. M(Ag) = 107.87 g/mol.- Calculate the charge passed. (1 mark)
- Calculate the moles of electrons. (1 mark)
- Calculate the mass of silver deposited. (1 mark)
Question 6 Brine electrolysis (2 marks)
Explain why electrolysis of concentrated aqueous sodium chloride gives hydrogen, not sodium, at the cathode. E°(Na⁺/Na) = −2.71 V; E°(H₂O/H₂, neutral to basic) is about −0.83 V.Question 7 Reading a nickel-silver cell (3 marks)
The diagram shows a standard nickel-silver cell.- Identify the anode and state the direction of electron flow. (1 mark)
- State how the mass of each electrode changes as the cell runs. (1 mark)
- Explain what happens to the voltage when [Ag⁺] falls. (1 mark)
Question 8 Free energy to potential (2 marks)
A reaction transfers 2 mol of electrons and has ΔG° = −193 kJ per mole of reaction.- Calculate E°. (1 mark)
- Say whether K is greater than 1 or less than 1 and justify. (1 mark)
