electrolysis

Question 1

define electrolysis

Answer 1

when electric current is used to break down a compound that is made of ions into simpler substances.

Question 2

what is the positive electrode called?

Answer 2

the anode

Question 3

what is the negative electrode called?

Answer 3

the cathode

Question 4

give 2 examples of materials that could be used to make electrodes and explain why they are used

Answer 4

• graphite or platinum

- these are unreactive materials which will not react with the electrolyte/products formed during electrolysis.

Question 5

define the electrolyte

Answer 5

what will be electrolysed

Question 6

which electrode are
1. cations
2. anions
attracted to?

Answer 6

1. cations are attracted to the cathode

2. anions are attracted to the anode.

Question 7

why must ionic substances be molten in order to be electrolysed?

Answer 7

so that the ionic lattice is broken down and the ions are free to move and carry the charge.

Question 8

what happens to the ions at the electrodes?

Answer 8

they become discharged

Question 9

does reduction or oxidation happen at the cathode and why?

Answer 9

reduction happens at the cathode as the positive ions gain electrons.

Question 10

does reduction or oxidation happen at the anode?

Answer 10

oxidation happens at the anode as the ions lose electrons.

Question 11

what does NILE PIG stand for?

Answer 11

negative ions lose electrons, positive ions gain.

Question 12

write an ionic equation to show how sodium is discharged

Answer 12

Na+1 + e- –> Na

Question 13

write an ionic equation to show how chlorine is discharged.

Answer 13

2Cl-1 -> Cl2 + 2e-

Question 14

give the ionic equation for the discharge of hydrogen

Answer 14

2H+ + 2e- -> H2

Question 15

give the ionic equation for the discharge of hydroxide ions

Answer 15

4OH- -> 2H2O + O2 + 4e-

Question 16

how is the order of discharge decided at the CATHODE?

Answer 16

• the least reactive ion is discharged

- hydrogen is less reactive than lead but more reactive than copper, silver, gold.

Question 17

name the order of discharge at the ANODE

Answer 17

carbonate (stay in solution)
nitrate (stay in solution)
sulphate (stay in solution)
HYDROXIDE, from water
chloride (discharged)
bromide (discharged)
iodide (discharged)