Question

In electrochemical cells, a spontaneous redox reaction is used to generate electric current. Conversely, in electrolysis, electric current is used to drive an otherwise non-spontaneous redox reaction. Electrolysis has numerous applications in industry. 

Now answer the following questions 

(i) Metals occur in the Earth‘s crust as minerals/ores. Name a few metals which can be extracted from their purified ores by electrolysis. 

(ii) What is electroplating? What are its uses?

Answer 1

(i) The sodium metal is extracted by electrolysis of fused sodium chloride. Sodium is obtained at the cathode while chlorine is produced at the anode.

Similarly, Mg is extracted from fused MgCl₂ and Ca from fused CaCl₂. 

Likewise, aluminium is extracted by electrolysis of fused alumina (Al₂O₃) using carbon electrodes. Since alumina is a bad conductor of electricity, therefore cryolite (Na₃AlF₆) is added to the fused alumina to make it conducting. The reactions taking place during electrolysis are:

(ii) The decomposition of one metal over another through electrolysis is called electroplating. The purpose of electroplating is 

a. To protect metals from rusting 

b. To decorate/beautify articles of iron, copper etc., by depositing silver or gold on them. 

To carry out electroplating, the article to be electroplated is made the cathode while the anode consists of the pure metal to be deposited and the electrolyte consists of some soluble salt of the metal to be deposited. During electrolysis, the pure metal from the solution gets deposited on the article and an equivalent amount of pure metal from the anode goes into the solution. By the process of electroplating, silver and gold plated artificial jewelry is prepared.