Topic 3 - Electrolysis (Paper 2)

Question 1

what is electrolysis?

Answer 1

the breaking down of a substance using electricity

Question 2

what happens during electrolysis?

Answer 2

an electric current is passed through an electrolyte, causing it to decompose

Question 3

what type of reactions happen in electrolysis?

Answer 3

oxidation and reduction reactions

Question 4

what happens to the positive ions in electrolysis?

Answer 4

the cations move towards the cathode and are reduced (gain electrons)

Question 5

what happens to the negative ions in electrolysis?

Answer 5

the anions move towards the anode and are oxidised (lose electrons)

Question 6

what happens as ions gain/lose electrons in electrolysis?

Answer 6

they form the uncharged substances and are discharged from the electrolyte

Question 7

can molten ionic compounds be electrolysed?

Answer 7

yes, as the ions can move freely

Question 8

what are molten ionic compounds broken up into in electrolysis?

Answer 8

their elements

Question 9

why would electrodes not take part in the reaction?

Answer 9

if they were made of an inert material

Question 10

what happens at the cathode when electrolysing molten lead bromide?

Answer 10

lead is reduced: Pb²⁺ + 2e⁻ = Pb

Question 11

what happens at the anode when electrolysing molten lead bromide?

Answer 11

bromide is oxidised: 2Br⁻ - 2e⁻ = Br₂

Question 12

what is an electrochemical cell?

Answer 12

a circuit made up of the anode, cathode, electrolyte, a power source and wires that connect the electrodes

Question 13

how would you set up an electrochemical cell for an aqueous solution?

Answer 13

1. get 2 inert electrodes
2. clean the electrode surface
3. place both electrodes into a beaker filled with electrolyte
4. connect the electrodes to a power supply

Question 14

what is different about electrolysing an aqueous solution compared to a molten solution?

Answer 14

there are hydrogen and hydroxide ions present as well as the ions from the ionic compound

Question 15

what happens at the cathode when electrolysing an aqueous solution?

Answer 15

both hydrogen and metal ions are present

Question 16

how do you decide which substance is electrolysed when electrolysing an aqueous solution? (cathode)

Answer 16

hydrogen gas will be produced if the metal is more reactive than hydrogen, the metal is produced if the metal is less reactive than hydrogen

Question 17

what happens at the anode when electrolysing an aqueous solution?

Answer 17

both hydroxide and ions from the compound are present

Question 18

how do you decide which substance is electrolysed when electrolysing an aqueous solution? (anode)

Answer 18

if halide ions are present, their molecules will form. if halides arent present, oxygen will be formed