Electrochemistry quiz

In a galvanic cell, oxidation occurs at the:

The SI unit of molar conductivity is:

The emf of a Daniell cell under standard conditions is:

Molar conductivity of a weak electrolyte increases steeply on dilution because:

The relation between Gibbs energy change and emf is:

Which of the following is a secondary cell?

The charge on one mole of electrons is approximately:

The potential of the standard hydrogen electrode is taken as:

The cell potential of a mercury cell is about:

During rusting of iron, the reaction at the cathode is:

What is the function of a salt bridge in a galvanic cell? (2 marks)

Write the Nernst equation for the electrode reaction M^n+(aq) + ne- -> M(s) at 298 K. (2 marks)

What is the cell constant? How is it determined? (2 marks)

Why does the conductivity of a solution decrease with dilution, while molar conductivity increases? (2 marks)

Write the reactions at the anode and cathode of a hydrogen-oxygen fuel cell. (2 marks)

State two advantages of fuel cells over conventional sources of energy. (2 marks)

Why can we not determine the limiting molar conductivity of a weak electrolyte by extrapolation? (2 marks)

Write the reactions taking place in a dry cell (Leclanche cell). (2 marks)

How many coulombs are required to reduce 1 mol of MnO4- to Mn2+? (2 marks)

Can a solution of CuSO4 be stored in a zinc vessel? Explain using E0 values (E0 Zn2+/Zn = -0.76 V, Cu2+/Cu = +0.34 V). (2 marks)

Calculate the standard emf of the cell Mg / Mg2+ // Ag+ / Ag, given E0 Mg2+/Mg = -2.37 V and E0 Ag+/Ag = +0.80 V. Calculate Delta G0 for the reaction (F = 96,500 C mol^-1). (3 marks)

Calculate the potential of a hydrogen electrode in contact with a solution of pH 10 at 298 K. (3 marks)

The conductivity of 0.20 M KCl solution at 298 K is 0.0248 S cm^-1. Calculate its molar conductivity. (3 marks)

How much charge is required to deposit 40.5 g of aluminium from molten Al2O3 (Al = 27 g/mol)? Express the answer in coulombs and faradays. (3 marks)

A current of 1.5 A passes through a solution of CuSO4 for 32 minutes 10 seconds. Calculate the mass of copper deposited (Cu = 63.5 g/mol). (3 marks)

Read the passage and answer the questions. A student set up a cell using a zinc rod in 1 M ZnSO4 and a copper rod in 1 M CuSO4, connected by a salt bridge. The voltmeter showed 1.10 V. When she applied an opposing external voltage greater than 1.10 V, the reaction reversed. (i) Write the cell representation. (ii) What happens when the external voltage equals 1.10 V? (iii) What type of cell does it become when the external voltage exceeds 1.10 V? (5 marks)

Read the passage and answer the questions. In an experiment, the molar conductivity of acetic acid was found to be 39.05 S cm2 mol^-1 at 0.001 M. The limiting molar conductivity of acetic acid is 390.5 S cm2 mol^-1. (i) Calculate the degree of dissociation. (ii) Calculate the dissociation constant. (iii) Why is acetic acid classified as a weak electrolyte? (5 marks)

Read the passage and answer the questions. A car battery consists of lead anodes and a grid of lead packed with lead dioxide as the cathode, dipped in about 38% sulphuric acid. When the car starts, the battery supplies current, and it is recharged when the engine runs. (i) Write the overall reaction during discharge. (ii) What happens during recharging? (iii) Why does the acid concentration fall during discharge? (5 marks)

Read the passage and answer the questions. Iron railings near the seashore rust faster than those inland. The rust is hydrated ferric oxide. Painting and galvanising are common methods of protection. (i) Write the anode and cathode reactions in rusting. (ii) Why is rusting faster near the sea? (iii) Explain how galvanising prevents rusting. (5 marks)

Read the passage and answer the questions. In the Apollo space programme, hydrogen-oxygen fuel cells provided electricity, and the water produced was used for drinking by the astronauts. (i) Write the overall cell reaction. (ii) Why are fuel cells more efficient than thermal power plants? (iii) State one limitation of fuel cells. (5 marks)

Draw a labelled diagram of the Daniell cell and explain its working. Derive the Nernst equation for the cell and explain how the emf changes with concentration. (6 marks)

Explain the variation of conductivity and molar conductivity with concentration for strong and weak electrolytes, with a labelled graph. State Kohlrausch's law and its applications. (6 marks)

State Faraday's laws of electrolysis. Draw a labelled diagram of an electrolytic cell for the electrolysis of aqueous CuSO4 and explain the products. (6 marks)

Describe the construction and working of the lead storage battery and the mercury cell with labelled diagrams and reactions. (6 marks)

Explain the electrochemical theory of corrosion with a labelled diagram, and describe four methods of preventing corrosion. (6 marks)