Question

Which of the following does not happen when nitric acid reacts with calcium carbonate?
(A) Carbon-dioxide is evolved
(B) Hydrogen is evolved
(C) Calcium nitrate is formed
(D) Water is formed

Answer 1

Nitric acid is a good acid and is a gas while calcium carbonate is solid. When nitric acid falls on the surface of calcium carbonate, a reaction occurs on the surface of carbonate itself leading to the formation of different compounds. Acids react with metal compounds to give salts and this happens in this case also.

Complete step by step solution:
-Acids are the compounds which donate their ${{H}^{+}}$ ions. They show a variety of reactions with different types of substrates like metals, bases, metal carbonates, metal nitrates, metal sulphates, etc.
-Nitric acid is a strong acid and is the parent acid of nitrogen with the valency of +5. Its chemical formula is $HN{{O}_{3}}$. Calcium carbonate is a form of carbonate. Carbonates have the general formula of $C{{O}_{3}}^{2-}$ . Whenever they react with acids, they form carbon-dioxide gas.
-Acids react with carbonates to give carbon-dioxide gas along with salt and water. Their reaction can be represented in the form as shown
$\begin{aligned} & acids+metal\text{ carbonates}\to \text{salts+carbon-dioxide+water} \\\ & \text{2HN}{{\text{O}}_{3}}\left( g \right)+CaC{{O}_{3}}\left( s \right)\to Ca{{\left( N{{O}_{3}} \right)}_{2}}\left( s \right)+C{{O}_{2}}\left( g \right)+{{H}_{2}}O\left( g \right) \\\ \end{aligned}$
-Normally when an acid reacts with metal, it forms a salt and hydrogen gas is evolved. But here we see that nitric acid is made to react with calcium carbonate and so, hydrogen gas is not evolved in this case.
$\begin{aligned} & Acid+metal\to salt+hydrogen \\\ & \text{2HN}{{\text{O}}_{3}}+Ca\to Ca{{\left( N{{O}_{3}} \right)}_{2}}+{{H}_{2}} \\\ \end{aligned}$
-So we can see that the compounds given in the question will react to give metal salts, carbon-dioxide and water. They will not give hydrogen gas. Hydrogen is formed when metals react with acids.

Thus the correct option is (B). Hydrogen is evolved.

Note: When the reaction occurs between the nitric acid and calcium carbonate. The rate of reaction is affected by the moisture present in the air. The reaction takes place on the surface of the carbonate itself. When moisture is present, then it is easier for the acid to get adsorbed on the surface of the carbonate and this enhances the reaction rate.