Egg shell contains calcium carbonate. When HCl is poured over egg shells, it dissolves in HCl to form calcium chloride and water and carbon dioxide is liberated with effervescence.

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egg shell is mainly composed of calcium carbonate.when dilute hydrochloric acid is added to it , it reacts to form salt ofCa + H2O + CO2.
CaCO3 + 2HCl ------> CaCl2 + H2O+ CO2
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Effects of HCl on an Egg Cell

When hydrochloric acid (HCl) is poured over an egg cell, several changes occur due to the corrosive nature of the acid. Here is a detailed explanation of what happens:

1. Shell Dissolution:
The outer shell of the egg is primarily composed of calcium carbonate. HCl reacts with calcium carbonate to produce carbon dioxide gas, water, and calcium chloride. As a result, the acid begins to dissolve the eggshell, causing it to break down.

2. Acidification of the Egg Contents:
As the shell dissolves, the HCl also starts to penetrate the egg's inner membrane, which is semi-permeable. This membrane allows small molecules, such as water and ions, to pass through while restricting larger molecules. The acid causes the pH of the egg contents to decrease, making it more acidic.

3. Denaturation of Proteins:
Proteins present in the egg, such as albumin, are sensitive to changes in pH. The acidic environment created by HCl denatures these proteins, altering their structure and functionality. Denaturation causes the proteins to lose their native shape, leading to the coagulation or solidification of the egg white.

4. Loss of Water Content:
As the proteins denature and coagulate, they trap water molecules within the egg. Consequently, the egg loses water content, resulting in shrinkage and a change in texture.

5. Formation of Calcium Chloride:
The calcium carbonate in the eggshell reacts with HCl to produce calcium chloride. This compound remains in the dissolved state in the acid solution.

6. Production of Carbon Dioxide Gas:
The reaction between HCl and calcium carbonate also generates carbon dioxide gas. This gas is released as bubbles during the dissolution of the eggshell, giving rise to effervescence.

In summary, pouring HCl over an egg cell leads to the dissolution of the eggshell, acidification of the egg contents, denaturation of proteins, loss of water content, formation of calcium chloride, and production of carbon dioxide gas. These changes result in the alteration of the egg's physical and chemical properties.