Everything Science Grade 12

CHAPTER 4. ELECTROCHEMICAL REACTIONS 4.3

The electrolysis of copper sulphate ESCBO

There are a number of examples of electrolysis.The electrolysis of copper sulphate is
just one.

Activity: The electrolysis of copper sulphate

Two copper electrodes are placed in a solution of blue copper sulphate and

are connected to a source of electrical current asshown in the diagram below.

The current is turned onand the reaction is left for a period of time.

+ –

+ –

positive anode negative cathode

copper electrode copper electrode

CuSO 4 solution

SO^24 − Cu2+

Observations:

• The initial blue colourof the solution remainsunchanged.


• It appears that copperhas been deposited on one of the electrodes but
  dissolved from the other.

Explanation:

• At the negative cathode, positively charged Cu2+ions are attracted to the
  negatively charged electrode. These ions gain electrons and are reduced
  to form copper metal,which is deposited onthe electrode. The half-
  reaction that takes placeis as follows:

Cu2+(aq) + 2e−→ Cu(s) (reduction half reaction)