Write a balanced chemical equation with the help of chemical symbols and formulas for the following reactions
(i) Zinc $ + $ silver nitrate$ \to $Zinc nitrate$ + $ silver
(ii) Copper oxide $ + $ hydrogen$ \to $Copper $ + $ water
(iii) Barium chloride$ + $ aluminium sulphate $ \to $Barium sulphate $ + $ aluminium chloride

Hint: The chemical equation is defined as the symbolic representation of compounds by their chemical formula. The entities present on the left side are called reactants and the entities present on the right side are called products. The number of atoms needs to be the same on both reactants and products side to balance the given equation.

Complete step by step solution:
We know that for a balanced chemical, the total number of atoms present on the left side of reactants is equal to the total number of atoms on the right side of the products side.
So for the first reaction of zinc with silver nitrate, we write the balanced chemical equation in the following way.
The balanced chemical equation is as follows
 $Zn + 2AgN{O_3} \to Zn{(N{O_3})_2} + 2Ag$
Where Zn and Ag are the chemical symbols of zinc and silver respectively.
Coming to the second reaction we have the reaction of copper oxide with hydrogen
The balanced chemical equation is as follows
$CuO + {H_2} \to Cu + {H_2}O$
Where Cu and H are chemical symbols of copper and hydrogen respectively
We have the next reaction as the reaction of barium chloride with aluminium sulphate.
The balanced chemical equation is as follows
$3BaC{l_2} + A{l_2}{(S{O_4})_3} \to 3BaS{O_4} + 2AlC{l_3}$
Where Ba, Al are the chemical symbols of barium and aluminium respectively

Note: The balancing of the chemical equation is based on the law of conservation of mass. It states that mass can neither be created nor be destroyed. It is of utmost importance to balance a chemical equation only we should remember that the number and mass of atoms on the reactants side should be equal to those on the products side.