Coca-Cola, like many other sodas, contains phosphoric acid which is the main culprit in dissolving eggshells. Here's what happens:

* Chemical Reaction: The phosphoric acid in Coca-Cola reacts with the calcium carbonate (CaCO3) in the eggshell.

* Decomposition: This reaction breaks down the calcium carbonate, forming calcium phosphate (Ca3(PO4)2), carbon dioxide (CO2) gas, and water (H2O).

* Dissolution: The calcium phosphate is soluble in water, so it dissolves in the Coca-Cola, leaving behind only the thin, flexible membrane that once held the egg yolk and white.

* Bubbles: You'll also see bubbles forming as the carbon dioxide gas is released during the reaction.

In essence, the phosphoric acid in Coca-Cola dissolves the calcium carbonate in the eggshell, leaving behind a soft, membrane-like structure.

Important Note: This experiment is a demonstration of the chemical properties of acids and carbonates. It is not recommended to drink Coca-Cola after it has been in contact with an eggshell.