Electrolysis

Question 1

What is an electrolyte?

Answer 1

An ionic compound in the molten state (or dissolved in water)

Question 2

What is electrolysis?

Answer 2

A process where electrical energy decomposes an electrolyte (from a DC supply)

Question 3

What are anions?

Answer 3

Negatively charged ions

Question 4

Which electrode do anions go to?

Answer 4

The oppositely charged (positively charged) electrode (the anode)

Question 5

What are cations?

Answer 5

Positively charged ions

Question 6

Which electrode do cations go to?

Answer 6

The oppositely charged (negatively charged) electrode (cathode)

Question 7

Where does reduction happen?

Answer 7

At the cathode

Question 8

What is reduction?

Answer 8

Gain of electrons

Question 9

What is oxidation?

Answer 9

Loss of electrons

Question 10

How do we know what is going to be formed at the cathode?

Answer 10

• When in solution hydrogen is produced unless the compound contains ions from a metal less reactive than hydrogen
• This is because hydrogen is more readily discharged than most metals
• When in the molten state, an element from the compound is always produced

Question 11

How do we know what is going to be formed at the anode?

Answer 11

• When in solution oxygen is produced from OH- ions unless the compound contains halide ions
• This is because oxygen is more readily discharged than most non-metals
• When in the molten state, an element from the compound is always produced

Question 12

How do you write a reduction half equation?

Answer 12

Metal ions + e- → metal

Question 13

How do you write an oxidation half equation?

Answer 13

Non metal ions → non-metal + e-

Question 14

What is the oxidation reaction at the anode in the electrolysis of copper oxide using copper electrodes?

Answer 14

Cu → Cu2+ + 2e-

Question 15

What is the half equation for when hydroxide ions are oxidised?

Answer 15

4OH- → 2H2O + O2 + 4e-