Question

Mention the difference between calcination and roasting How these
processes are used in the extraction of zinc ? Explain with the help of
chemical equations. After these processes, is reduction necessary to obtain
zinc ? Why?​

Answer 1

Answer:

Explanation:

Ans. :  

Ë Carbonate ores are converted into oxides by heating strongly in limited air. This process is known as calcination.  2 1  

Ë Sulphide ores are converted into oxides by heating strongly in the presence of excess of air. This process is known as roasting.  2 1 Ë When ZnCO3 undergoes calcination ZnO is formed.  ZnCO3 ( s )  ⎯ ⎯ ⎯→⎯ heat  ZnO ( s ) + CO2 ( g ). 1  

Ë When ZnS undergoes roasting, ZnO is formed.  2 ZnS ( s ) + 3O2 ( g ) ⎯ ⎯ ⎯→⎯ heat  2 ZnO ( s ) + 2 SO2 ( g ). 1 Ë After these processes reduction is necessary.  2 1  

Ë Because zinc oxide is then reduced to zinc using suitable reducing agent.  2