Question

Zinc granules give ${H_2}$ gas when treated with dilute solution of :
A.${H_2}S{O_4}$
B.$HCl$
C.$NaOH$
D.all of these

Answer 1

When any metal reacts with acid hydrogen gas is evolved in most of the cases . It is an exothermic reaction in which heat is evolved in the atmosphere .

Complete step by step answer:
In chemistry, some elements are called amphoteric which means they react with acids as well as base. 'Amphi' is a greek word meaning both which here means both acidic and basic.
The oxide of zinc metal is amphoteric in nature ,that is, it reacts with acid as well as a base.
In case of reaction with dilute sulphuric acid $({H_2}S{O_4})$, the product is zinc sulphate and hydrogen gas is released. This is because zinc is more reactive than hydrogen so it displaces it from the solution of sulphuric acid and forms zinc sulphate liberating hydrogen gas.
$Zn + {H_2}S{O_4} \to ZnS{O_4} + {H_2}$
In case of reaction with dilute hydrochloric acid $(HCl)$, the products are zinc chloride and bubbles are evolved indicating the liberation of hydrogen gas. It is a replacement reaction where zinc replaces hydrogen from dilute hydrochloric acid solution and forms zinc chloride with hydrogen gas liberation.
$Zn + HCl \to ZnC{l_2} + {H_2}$
In case of reaction with dilute sodium hydroxide solution $(NaOH)$, the product is sodium zincate and hydrogen gas is released.
$Zn + NaOH \to N{a_2}Zn{O_2} + {H_2}$
Now we see that zinc is amphoteric in nature, that is, it reacts with acid as well as base. Hence all the options A , B and C are correct .
Therefore, option D is correct .

Note: Some metals do not evolve hydrogen gas when treated with acids , the reason behind this is the low reactivity of metals such as mercury . We can find out which metals react with acids to evolve hydrogen gas and which don't by looking at the reactivity series .