The representation of a chemical reaction in the form of substances is known as a chemical equation. The equation in which the number of atoms of all the molecules is equal on both sides of the equation is known as a balanced chemical equation.
(1) MnO2 + HCl → MnCl2 + H2O + Cl2
The balanced chemical equation is
MnO2 + 4 HCl → MnCl2 + 2H2O + Cl 2
By means of a stoichiometry, 1 mol of manganese dioxide reacts with 4 mol of HCl (hydrochloric acid) to form 1 mol manganese chloride 1 mol of chloride & 2 mol of water.
(2) C2H4 + O2→ CO2 + H2O
The balanced equation is
C2H4 +3O2 → 2CO2 + 2H2O
Via stiochiometery, 1 mol of ethene reacts with 3 mol oxygen to produce to 2 mol of carbon dioxide and 2 mol of water.