Unit 2.3 (2) - Metals and their extraction

Question 1

What happens in the electrolysis of water and what does the observation prove about the composition of water?

Answer 1

Electrolysing water splits it up into H2 and O2. Double the volume of hydrogen is produced as oxygen, showing that there are twice as many hydrogen atoms as oxygen in water (H20).

Question 2

What happens in the electrolysis of an aqueous solution where the solution contains a low-reactivity metal?

Answer 2

Metals which are lower in the reactivity series than hydrogen are formed at the cathode.

Question 3

What happens in the electrolysis of an aqueous solution where the solution contains a higher-reactivity metal?

Answer 3

If the metal’s reactivity is higher than that of hydrogen, then hydrogen forms at the cathode, rather than the metal.

Question 4

In electroplating by electrolysis, are the electrodes made of and what solution is used as the electrolyte?

Answer 4

The negative electrode (cathode) is the object to be plated, the positive electrode (anode) is made out of the metal which is being used to ‘plate’ with, and the electrolyte is a solution of the plating metal.

Question 5

In purification of copper by electrolysis, are the electrodes made of and what solution is used as the electrolyte?

Answer 5

The positive electrode (anode) is made from impure copper and the negative electrode (cathode) is made from pure copper; the electrolyte is a solution containing copper compounds (e.g. CuSO4).

Question 6

What happens in the purification of copper by electrolysis?

Answer 6

Pure copper forms on the cathode (pure copper), increasing its size, while the anode (impure) shrinks, as it has deteriorated, leaving ‘anode sludge’ at the bottom of the beaker.

Question 7

What is the primary reason for the siting of extraction plants near the coast?

Answer 7

Import of raw materials (not export of products).