Question

What happens when nitric acid is added to the egg shell? Give a reason for your observation.

Answer 1

Egg shell is hard to touch and is made up of a chemical compound like calcium carbonate, it is a salt.
When the metal carbonates react with acidic compounds like nitric acid or Hydrochloric acid liberates salt in which the carbonate anion is replaced by another group from the acidic compound and water gases like carbon dioxide.

Complete answer:
Egg consists of a semi fluid in yellow and white color.
This semi fluid is present in a hard shell called an egg shell.
It is made up of a metal carbonate, in the egg shell the calcium carbonate will be present. Calcium carbonate consists of calcium ions with a positive charge and carbonate ions with negative charge.
In this metal carbonate, calcium is a cation and carbonate is anion.
Generally, metal carbonates and hydrogen carbonates react with acids that liberate salt, water and carbon dioxide.
Thus, calcium carbonate present in egg shells, when reacted with nitric acid liberates calcium nitrate, salt, water and a gas like carbon dioxide.
The chemical reaction involved in the above process is
$CaC{O_3} + 2HN{O_3} \to Ca{\left( {N{O_3}} \right)_2} + {H_2}O + C{O_2}$
The carbon dioxide is liberating with effervescences and turns lime water into milky.
It is a burning gas and also a glowing splint.
Thus, when the egg shell is treated with nitric acid the above chemical reaction can be observed.

Note:
The metal carbonates treated with nitric acid liberates a salt like metal nitrites.
Different metal carbonates react with different acids to form different salts.
The gas like carbon dioxide and water can also be evolved in the above reaction.