When hydrochloric acid (HCl) and sodium ethanoate (CH3COONa) are combined, a chemical reaction takes place. This reaction is known as an acid-base reaction, and it results in the formation of a new compound, sodium chloride (NaCl), along with the release of ethanoic acid (CH3COOH).

The overall chemical equation for this reaction can be written as:

HCl + CH3COONa → NaCl + CH3COOH

In this reaction, HCl acts as the acid, and CH3COONa acts as the base. The hydrogen ion (H+) from HCl combines with the acetate ion (CH3COO-) from CH3COONa to form ethanoic acid, while the sodium ion (Na+) from NaOH and the chloride ion (Cl-) from HCl combine to form sodium chloride.

The reaction between hydrochloric acid and sodium ethanoate is an example of a neutralization reaction. In such reactions, an acid and a base react in stoichiometric amounts to form a salt and water. Neutralization reactions are often used to control the pH of solutions, as they can be used to either increase or decrease the acidity or basicity of a solution.