Question

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

Answer 1

Hint: We can solve this question with the concept of reaction of metals with acids. Most of the metal has when react with the acids remove hydrogen gas i.e. the concept which we used in this question. This reaction is a type of exothermic reaction. In such a type of reaction, the heat is produced after the reaction. General reaction is shown below:
Acid + metal $ \to $salt + hydrogen.

Complete step by step answer:
When acids react with metals, salt of metal and hydrogen gas produces. In this type of reaction, we do not get ${H_2}O$.

For the given question, we one by one check all the options that will produce hydrogen gas after the reaction.
(A) when zinc granules react with dilute sulphuric acid $({H_2}S{O_4})$, it will produce zinc sulphate and hydrogen gas. The reaction is as follows: $Zn + {H_2}S{O_4} \to ZnS{O_4} + {H_{2(g)}}$.
(B) when zinc granules are treated with hydrochloric acid $(HCl)$, we find that zinc chloride $(ZnCl)$ and hydrogen gas formed and the reaction is here: $Zn + 2HCl \to ZnC{l_2} + {H_{2(g)}}$.
(C) Similarly, when the zinc reacts with $NaOH$ (this reaction occurs with water), sodium zincate$\left( {N{a_2}Zn{{(OH)}_4}} \right)$ and hydrogen gas formed. The reaction is shown below:

$Zn + 2{H_2}O + NaOH \to N{a_2}Zn{(OH)_4} + {H_{2(g)}}$
Hence, we see that all the acids produce hydrogen gas after reaction with zinc granules. So the correct answer of the question is option D i.e. all the above acids produce ${H_2}$ gas.
So, the correct answer is “Option D”.

Note: There are some metals which do not form ${H_2}$ gas after reaction with acids due to its low reactivity i.e. mercury. We have a series to find which metals can react with acid and this series is called reactivity series of metals.