required prac 3

• Investigating what happens when aqueous solutions undergo electrolysis

  1. Pour approximately 50 cm^3 of copper(II) chloride solution into a beaker

  2. Place a plastic petri dish with two holes over the beaker

  3. Insert a carbon graphite rod into each hole (electrodes)

  4. Attach crocodile leads to the rods and connect to a low-voltage power supply

  5. Select 4 volts on the power supply and switch it on
• Electrodes


  • Carbon graphite rods are unreactive (inert)
  • The two electrodes must not touch each other to avoid a short-circuit
• Copper is less reactive than hydrogen


  Copper is discharged at the cathode
• Electrolyzing a solution containing a halide ion


  The halogen is discharged at the anode
• Holding a piece of damp blue litmus paper near the anode shows it becomes bleached, proving the gas is chlorine
• When electrolyzing copper(II) chloride solution, copper is discharged at the cathode and chlorine gas is discharged at the anode
• Investigating electrolysis of sodium chloride solution

  1. Pour approximately 50 cm^3 of sodium chloride solution into a beaker

  2. Turn on the low-voltage power supply
• Sodium is more reactive than hydrogen


  Hydrogen gas is discharged at the cathode
• Hydrogen gas can be collected and tested with a lit splint, producing a squeaky pop
• Blue litmus paper


  Turns pink in the presence of an acid
• Red litmus paper


  Turns blue in the presence of a base
• Litmus paper pH indicator

  Changes color in response to acidity or basicity
• Chlorine gas oxidizing agent

  Strong oxidizing agent produced during electrolysis