Balance the following chemical equations :
(a) HNO₃ + Ca (OH)₂ → Ca (NO₃)₂ + H₂O
(b) NaOH + H₂SO₄ → Na₂SO₄ + H₂O
(c) NaCl + AgNO₃ → AgCl + NaNO₃
(d) BaCl₂ + H₂SO₄ → BaSO₄ + HCl

A balanced chemical equation has the number of atoms of each element equal on both the left and right sides of the reaction. It has equal masses of various elements in the reactants and products. The '+' is read as 'reacts with' and the arrow '' means 'produces'. The chemical formulas on the left represent the starting substances, called reactants.

Example: $Ca( OH)_{2} \ ( aq) \ +CO_{2\ }( g) \ \rightarrow \ CaCO_{3} \ ( s) \ +\ H_{2} O\ ( l)$

(a) $2HNO_3 + Ca(OH)_2 → Ca(NO_3)_2 + 2H_2O$

(b) $2NaOH + H_2SO_4 → Na_2SO_4 + 2H_2O$

(c) $NaCl + AgNO_3 → AgCl + NaNO_3$

(d) $BaCl_2 + H_2SO_4 → BaSO_4 + 2HCl$