Applications of Electrolysis

Question 1

What are the 3 applications of electrolysis?

Answer 1

Electroplating
Purification of copper
Electrolysis of sodium chloride

Question 2

Why are metals electoplated?

Answer 2

To improve appearance and resistance to corrosion

Question 3

What are the 3 rules of electroplating?

Answer 3

Object that is to be electroplated = made the cathode
Anode made from the metal that will provide the coating layer
Electrolyte = solution containing metal ions of the metal providing the electroplating layer

Question 4

Describe the purification of copper.

Answer 4

Copper normally extracted from copper ore by reduction using carbon; produces copper that is impure (includes silver, platinum, gold and zinc)

Question 5

What is the major use of copper?

Answer 5

Electrical wiring - for this use, it needs to be 99.9% pure to conduct electricity efficiently

Question 6

What are the 3 rules of purification of copper?

Answer 6

Impure copper is the anode
Pure copper is the cathode
Electrolyte is copper sulfate solution

Question 7

What are the reactions at the anode and cathode for the purification of copper?

Answer 7

At the anode:

Cu(s) -> Cu 2+(aq) + 2e (oxidation reaction)
Copper loses electrons; go into solution as Cu 2+ ions
Anode loses mass
Impurities fall to bottom of the cell -> known as sludge / slime

At the cathode:

Cu 2+(aq) + 2e -> Cu (s)
Cu 2+ ions attracted to cathode where they gain electrons forming Cu atoms
Layer of pure copper builds up on cathode; cathode gains mass

Question 8

Describe the electrolysis of concentrated NaCl solution.

Answer 8

Basis of chlor-alkali industry; produces hydrogen (H), chlorine (Cl) and NaOH (sodium hydroxide)

Question 9

What is the reaction for the electrolysis of concentrated NaCl solution?

Answer 9

2NaCl (aq) + 2H2O (l) -> 2NaOH (aq) + Cl2 (g) + H2 (g)
Brine -> sodium hydroxide + chlorine + hydrogen

Question 10

What are the reactions at the anode and cathode for the electrolysis of concentrated NaCl solution?

Answer 10

At the anode:

2Cl- (aq) -> Cl2 (g) + 2e (oxidation reaction)

At the cathode:

2H+ (aq) + 2e -> H2 (g)

NaOH is product

Question 11

Give 3 examples for the uses of hydrogen.

Answer 11

Nylon
Hydrogen peroxide
Margarine

Question 12

Give 3 examples of the uses of chlorine.

Answer 12

Plastics
Solvents
Weed killers

Question 13

Give 3 examples of the uses of sodium hydroxide.

Answer 13

Soap
Detergents
Textiles