Electrolysis

Question 1

What is electrolysis?

Answer 1

Electrolysis is the breaking down of a substance using electricity
An electric current is passed through an an electrolyte (molten or dissolved ionic compound), causing it to decompose

Question 1

What state does the electrolyte have to be in electrolysis - why?

Answer 1

Molten (liquid) or aqueous so that the ions are free to move to the electrodes

Question 2

What does inert mean?

Answer 2

Unreactive

Question 3

What are the electrodes in electrolysis made of - why?

Answer 3

Unreactive (inert) substances, so that they do not react with the electrolyte or the products made
e.g. graphite or platinum

Question 4

What happens during electrolysis?

Answer 4

Positive ions (cations) in the electrolyte move towards the negative electrode (cathode) and are reduced (gain electrons)

Negative ions (anions) in the electrolyte move towards the positive electrode (anode) and are oxidised (lose electrons)

As the ions gain or lose electrons, they form uncharged substances and are discharged from the electrolyte

Question 5

What’s a disadvantage of electrolysis?

Answer 5

Requires a large amount of energy to melt the compounds

Question 6

What’s oxidation?

Answer 6

Loss of electrons

Question 7

What’s reduction?

Answer 7

Gain of electrons

Question 8

Has reduction or oxidation taken place: Be forming a Be²⁺

Answer 8

oxidation:
- Be has lost electrons to become positively charged
- Oxidation Is Loss of electrons (OIL RIG)

Question 9

What’s the half equation for reduction of Chlorine?

Answer 9

Cl + e⁻ —-> Cl⁻

Question 10

Does reduction or oxidation occur at the cathode?

Answer 10

Reduction

Question 11

Does reduction or oxidation occur at the anode?

Answer 11

Oxidation

Question 12

What happens at the cathode during electrolysis of aqueous solution?

Answer 12

• H⁺ ions from the water, and metal ions are attracted to the cathode
• If the metal is more reactive than hydrogen, hydrogen gas will be produced
• If the metal is less reactive than hydrogen, a solid layer of pure metal will be produced
  IF COPPER OR SILVER IS PRESENT, COPPER OR SILVER WILL BE PRODUCED

Question 13

What happens at the anode during electrolysis of aqueous solution?

Answer 13

• If OH- and halide ions (group 7) are present at the anode, molecules of the halides will be formed
• If no halide ions are present, oxygen will be formed