During the reaction of some metals with dilute hydrochloric acid, following observations were made.
(a) Silver metal does not show any change
(b) The temperature of the reaction mixture rises when aluminium (Al) is added
`(c)`The reaction of sodium metal is found to be highly explosive
(d) Some bubbles of a gas are seen when lead (Pb)is reacted with the acid Explain these observation giving suitable reasons.

Explanation

(i) The temperature of the reaction mixture rises when aluminium is added because it is an exothermic reaction.
(ii) Reaction of sodium metal is found to be highly explosive because it is an exothermic reaction.
(iii) When lead is treated with hydrochloric acid, bubbles of hydrogen gas are evolved.
`Pb(s)+2HCl(aq)rarrPbCl_(2)(aq)+H_(2)(g)`