ELECTROCHEMISTRY

A current is passed through two cells connected in a series. The first cell contains XSO₄ (aq) while the second cell contains Y₂SO₄ (aq). The relative atomic masses of X and Y are in the ratio 1:2. What is the ratio

mass of X liberated : mass of Y liberated?

• 1:1

• 1:2

• 1:4

• 2:1

When 5 mol of electrons are passed through a molten aluminium salt, what is the maximum mass of aluminium formed at the cathode? [Ar: Al, 27]

• 5.4 g

• 16.2 g

• 27 g

• 45 g

During an industrial electrolysis to obtain aluminium, both hydrogen and carbon monoxide may be evolved as undesirabe by-products.

What are the sources of these gases?

1. source of HF (g) = ?

2. source of CO (g) = ?

• 1. the bauxite 2. the anode

• 1. the bauxite 2. the cathode lining

• 1. the cryolite 2. the anode

• 1. the cryolite 2. the bauxite

In the extraction of aluminium by electrolysis, it is necessary to dissolve aluminium oxide in cryolite. Give the chemical formula of cryolite.

If a cell is connected using magnesium and manganese as electrodes as shown in the above diagram.

Which metal will act as the anode?

• Mg

• Mn

Describe the reaction occur in the above cell.

Diaphragm cell is an electrolytic cell used in industry to manufacture chlorine. What is brine?

What is the function of the asbestos diaphragm in the cell?

• to allow ions in the anode and cathode compartment to diffuse through freely.

• as a divider to separate the anode and cathode compartments.

• to separate the chlorine and hydrogen gas spaces.

• allows a through flow of brine from anode to cathode.

Which of the following statements about Daniell cell is true?

• The Daniell cell produces an electromotive force of -1.1 V.

• Electrons flow from anode to cathode in the external circuit.

• The anode is charged positive.

• The mass of cathode decreases.

A current of 8.0A is passed for 100 mins through molten aluminum oxide using inert electrodes. What will be the approximate volume of gas liberated?

• 2.6 dm³

• 3.2 dm³

• 3.0 dm³

• 2.8 dm³