Required Practical 3: Electrolysis

Question 1

How do we investigate what happens when copper (II) chloride solution undergoes electrolysis?

Answer 1

1) First we pour 50cm³ of copper (II) chloride solution into a beaker.
2) We then place a plastic petri dish over the beaker and it should have 2 holes.
3) We now insert a carbon graphite rod into each hole and they must no touch each other otherwise it would produce a short-circuit.
4) Next we attach crocodile leads to the rods and connect them to the terminals of a low-voltage power supply.
5) We now select 4V on the power supply and switch it on.
6) If we hold a piece of damp blue litmus paper near the anode then it becomes bleached proving there is chlorine at the anode. At the cathode we then get copper discharged at the cathode.

Question 2

How do we investigate what happens when sodium chloride solution undergoes electrolysis?

Answer 2

1) First we pour 50cm³ of sodium chloride solution into a beaker.
2) We then place a plastic petri dish over the beaker and it should have 2 holes.
3) We now insert a carbon graphite rod into each hole and they must no touch each other otherwise it would produce a short-circuit.
4) Next we attach crocodile leads to the rods and connect them to the terminals of a low-voltage power supply.
5) We now select 4V on the power supply and switch it on.
6) At the anode we see bubbles being produced and this gas bleaches damp blue litmus paper meaning chlorine is at the anode. And at the cathode, we also see bubbles at the cathode and that is hydrogen as we are electrolysing sodium chloride solution and since sodium is more reactive than hydrogen, hydrogen gas is discharged at the cathode we can test its hydrogen with a lit splint and hydrogen gas produces a squeaky pop.