Electrolysis of Copper Sulfate

• The copper ions (Cu²⁺) will go into the electrolyte solution of copper sulfate.
• The Cu²⁺ ions will be attracted to the cathode and pure copper will form.
  • Cu²⁺_(aq) + 2e^- → Cu_(s)

• The impurities of the anode will fall to the bottom of the beaker.
• When the mass of the cathode is constant, the purification process is complete.

To measure the mass of copper formed on the cathode over time:

• Record the initial mass of the electrodes. The cathode must be cleaned for the copper to stick to it
• Use a variable resistor because the current may vary during the process. It should be kept constant.

• You should wash electrodes to remove any copper sulfate. You should then dry them.
• You should also wash the electrodes with a more volatile solvent to make them dry faster. You could use propanone, for instance.

• Measure the final mass of the electrodes to work out the change in mass: change in mass = final mass - initial mass.