Chemical reaction

A chemical reaction is a process that results in the transformation of one set of chemical substance to another.Chemical reactions may be reversible or irreversible.

In a reversible reaction,the products of the reactions can be converted back to the reactants.Whereas in an irreversible reaction, the products of the reactions cannot be converted back to the reactants.

For example, Ammonium  chloride which has been converted to ammonia and hydrogen chloride by heating can be reversed back to ammonium chloride when cold.

Example of irreversible reaction is given below:
NaOH + HCl –> NaCl + H₂O + 13.7 kcal