ES.3

Question 1

How can chlorine be made to be used for bromine extraction?

Answer 1

Chlorine can be made industrially by electrolysis of concentrated solution of sodium chloride.

Question 2

What is electrolysis?

Answer 2

It is the process of decomposing a compound using an electric current.

Question 3

What are additional products (products other than the ones you want) called in a reaction?

Answer 3

Co-products.

Question 4

What halogen is seaweed a source of?

Answer 4

Iodine.

Question 5

What state must the compound be in for electrolysis to be possible and why?

Answer 5

It must molten or aqueous. This is because electrolysis requires free moving electrons to complete the circuit.

Question 6

What are positively charged ions called?

Answer 6

Cation.

Question 7

What are negatively charged ions called?

Answer 7

Anion.

Question 8

What is the positive electrode called?

Answer 8

Anode (attracts anion).

Question 9

What is the negative electrode called?

Answer 9

Cathode (attracts cation).

Question 10

What happens at the positive electrode (anode)?

Answer 10

Anions lose electrons and are oxidised.

Question 11

What happens at the negative electrode (cathode)?

Answer 11

Cations gain electrons and are reduced.

Question 12

What are the electrodes normally made of?

Answer 12

Inert material like graphite.

Question 13

What are the general products of electrolysis of molten salt?

Answer 13

Cathode: metal.
Anode: non-metal (apart from hydrogen).

Question 14

Why do we electrolyse some compounds in aqueous form rather than molten?

Answer 14

Some salts have very high melting points so it’s very expansive to melt it.

Question 15

Why could there be different unexpected products when electrolysising solutions?

Answer 15

Because the water in the solution will competes with the ions from the salt at electrodes.

Question 16

What can happen to water at the cathode?

Answer 16

Water can be reduced to make hydrogen gas and hydroxide ions.

Question 17

What can happen to water at the anode?

Answer 17

Water can be oxidised to make oxygen gas adn hydrogen ions.

Question 18

What happpens at the cathode if the metal in the salt is from group 1 or 2 (reactive metal)?

Answer 18

Metal ions remain in the solution while hydrogen ions are reduced to form hydrogen gas.

Question 19

What happens at the cathode if the metal in the salt is less reactive metal like copper and zinc?

Answer 19

The metal ions will be reduced and that metal will form at the cathode and hydrogen ions are left in the solution.

Question 20

What happens at the anode if the salt contained halogen?

Answer 20

As halide ions have greater tendency to be oxidised than hydroxide ions, halide ions will be oxidised and halogen will be produced at the anode.

Question 21

What happens at the anode if the salt contained nitrate or sulfate?

Answer 21

As nitrate and sulfate ions have less tendency to be oxidised than hydroxide ions, hydroxide ions will be oxidised and oxygen will be produced at the anode.