Question

Draw a labelled diagram of electrolytic refining of copper.

Answer 1

Part 1: Electrolytic refining:

Electrolytic refining is the process of refining a metal (mainly copper) by the process of electrolysis. During electrolysis, a large chunk or slab of impure metal is used as the anode with a thin strip of pure metal at the cathode. In the setup, an electrolyte (metal salt aqueous solution) depending on the metal is often used.

After electrolysis, the clean or pure metal is formed at the cathode when the electrical current of a sufficient voltage is applied by dissolving impure metal at the anode.

Part 2: Electrolytic refining of copper: A block of impure copper is taken as an anode or positive electrode. Copper sulfate which is acidified with sulphuric acid is used as a graphite-coated electrolyte along with pure copper tubes, as a cathode or negative electrode. In this phase of electrolysis copper sulfate divides into a positive ion of copper (${\mathrm{Cu}}^{2+}$) and a negative ion of sulfate (${\mathrm{SO}}_4^{-}$). The positive copper ion (${\mathrm{Cu}}^{2+}$) or cations travel towards the negative electrode made of pure copper where it absorbs the electrons from the cathode. A copper atom is deposited on the cathode’s graphite layer.

In the experiment, the impure copper metal is made anode and the pure metal of copper is the cathode, and copper sulfate ( ${\mathrm{CuSO}}_4$ ) is an electrolyte. Pure copper from electrolyte deposited on cathode, soluble impurities go into solution and insoluble impurities remain in the solution and deposited at bottom of the anode.