Why we write Hcl as 2HCL in the equation??

And others also like 2AL at the place of AL

A chemical equation is a written symbolic representation of a chemical reaction. The reactant chemical(s) are given on the left-hand side and the product chemical(s) on the right-hand side. The two are connected with an arrow leading from the left to the right, symbolizing the reaction. The law of conservation of mass states that no atoms can be created or destroyed in a chemical reaction, so the number of atoms that are present in the reactants has to balance the number of atoms that are present in the products.