C5. Electricity & Chemistry

Question 1

Refining of metal

Answer 1

Anode: impure metal
Cathode: pure metal
Electrolyte: solution of the pure metal

Question 2

Electroplating of metal

Answer 2

Anode: plating metal
Cathode: object
Electrolyte: solution of the plating metal

Question 3

How do you achieve an even and thin layer of coating (electroplating)?

Answer 3

1. Use a small current, by using a resistor
2. Rotate the object you are electroplating slowly
3. Immerse the object completely in the electrolyte

Question 4

Uses of aluminium (extraction of Al)

Answer 4

1. Packaging - drinks cans, foil wrapping, foil containers
2. Transport - aeroplanes
3. Overhead electrical cables
4. As a building material
5. For kitchen utensils

Question 5

Uses of chlorine (extraction of Cl from brine)

Answer 5

1. For making bleach
2. Producing hydrochloric acid
3. Sterilising drinking water & swimming pools
4. Making pesticides
5. Making medical drugs
6. Making the plastic PVC

Question 6

Uses of sodium hydroxide (extraction of NaOH from brine)

Answer 6

1. Making detergents, washing powder & soaps
2. Making textile dyes
3. In the extraction of aluminium
4. Making paper
5. Making ceramics (eg. tiles, furnace bricks)

Question 7

Uses of hydrogen (extraction of H2 from brine)

Answer 7

1. Making nylon
2. Making hydrogen peroxide
3. To ‘harden’ vegetable oils to make margarine
4. As a fuel in hydrogen fuel cells

Question 8

How do you strengthen aluminium for use in overhead power lines and electrical cables?

Answer 8

Wrap aluminium around a central core of steel

Question 9

What are ceramic discs used for?

Answer 9

Ceramic discs are used to prevent the electric current passing from cables to pylons

Question 10

3 reasons why molten cryolite is used during extraction of aluminium from bauxite by electrolysis

Answer 10

1. to reduce cost
2. to lower the operating temperature
3. to increase the conductivity