1) the substances on the left side are the reactants and the substances on the right are the products
2) the coefficients are 6,2,3
The subscripts are 2,3
3) 6 H on the left : 6H on the right
4) 6 Cl on the left : 6 Cl on the right
5) 2 Al on the left : 2 Al on the right
6) The law of conservation of matter says that in chemical reactions, the total mass of the products must equal the total mass of the reactants.