Give reasons for the following :

(a) Sodium and potassium are stored in kerosene.

(b) Copper cannot displace zinc from its salt solution (zinc sulphate solution).

a) sodium and potassium are stored in kerosene.

Sodium and potassium are the most reactive metals. They are stored in kerosene because they react very vigrously with air and water because of the presence of oxygen. If they come in contact with oxygen then it will react and will form sodium hydroxide. And kerosene is a alkanes and don't react much.. that's why sodium and potassium are stored in kerosene.

(b) copper cannot displace zinc from its zinc sulphate solution.

Yes, copper cannot displace zinc from it's zinc sulphate solution. As we know zinc is more reactive metal as compared to copper. And in displacement reaction, a more reactive metal displaces a less reactive metal from its solution. But copper is less reactive than zinc so how it can displace zinc .. that's why copper cannot displace zinc from it's zinc sulphate solution.