Chemistry - 6 Electrolysis - Required Practical 3: Electrolysis

Aims:

  • observe the products of electrolysis and compare between two different solutions

Risk Assessment:

  • chemicals can damage eyes

  • gaseous products (especially chlorine) could cause shortness of breath

  • chlorine is toxic

Safety:

  • wear safety goggles

  • warn asthmatics

  • carry out experiment in a fume cupboard

Equipment:

  • 0.5 mol/dm³ copper (II) chloride solution

  • 0.5 mol/dm³ sodium chloride solution

  • Petri dish lid with bored holes

  • two carbon rod electrodes with support bungs

  • two crocodile/4 mm plug leads

  • low voltage power supply

  • blue litmus paper

  • forceps

  • beaker

Control variables:

n/a

Independent variable:

n/a

Dependent variable:

n/a

Method:

Copper (II) chloride

  1. Place 50 cm³ of copper (II) chloride solution in a beaker and cover it with the Petri dish lid

  2. Insert the carbon rods into the holes so that they are submerged in solution

  3. Attach crocodile leads to the rods and then to the power supply. Switch the power supply on at 4 V

  4. Closely observe the electrodes for discharged products (copper at cathode; chlorine gas at anode)

  5. Hold damp blue litmus paper near the anode. It should bleach; this proves the gas is chlorine

Sodium chloride

  1. Place 50 cm³ of sodium chloride solution in a beaker and cover it with the Petri dish lid

  2. Insert the carbon rods into the holes so that they are submerged in solution

  3. Attach crocodile leads to the rods and then to the power supply. Switch the power supply on at 4 V

  4. Closely observe the electrodes for discharges products (hydrogen gas at cathode; chlorine gas at anode)

  5. Hold damp blue litmus paper near the anode. It should bleach; this proves the gas is chlorine

  6. Collect the gas from the cathode and hold a lit splint near it. It should produce a squeak/pop; this proves the gas is hydrogen

Calculations/graphing:

n/a