Question

Write a balanced chemical equation with state symbol for the following reactions:
(i)- Solution of barium chloride and sodium sulfate in water react to give insoluble barium sulfate and the solution of sodium chloride.
(ii)- Sodium hydroxide solution (in water) reacts with a hydrochloric acid solution (in water) to produce sodium chloride solution and water.

Answer 1

Barium chloride is made up of three ions, so the formula is $BaC{{l}_{2}}$. Sodium sulfate is made up of three ions, so the formula is $N{{a}_{2}}S{{O}_{4}}$. Sodium hydroxide is made up of two ions, so the formula is $NaOH$. Hydrochloric acid is made up of two ions, so the formula is $HCl$.

Complete answer:
(i)- When the solution of barium chloride and sodium sulfate reacts to form barium sulfate and sodium chloride. So the formula of barium chloride, sodium sulfate, barium sulfate and sodium chloride are $BaC{{l}_{2}},\text{ N}{{\text{a}}_{2}}S{{O}_{4}},\text{ BaS}{{\text{O}}_{4}},and\text{ NaCl}$ respectively. So the reaction will be:
$BaC{{l}_{2}}+N{{a}_{2}}S{{O}_{4}}\to BaS{{O}_{4}}+NaCl$
This reaction is not balanced. On the reactant side, there are 2 sodium and chlorine atoms but on the product side, there is only one sodium and a chlorine atom. So by multiplying the sodium chloride with 2, we can get a balanced equation.
$BaC{{l}_{2}}+N{{a}_{2}}S{{O}_{4}}\to BaS{{O}_{4}}+2NaCl$
(ii)- When the sodium hydroxide and hydrochloric acid react with each other, there is the formation of sodium chloride and water. So the formula of sodium hydroxide, hydrochloric acid, sodium chloride and water are $NaOH,\text{ HCl, NaCl, and }{{\text{H}}_{2}}\text{O}$ respectively. So the reaction will be:
$NaOH+HCl\to NaCl+{{H}_{2}}O$
All the atoms on both sides are the same, so the equation above is balanced. No change is needed.

Note:
Whenever balancing of the equation is required, then first balance the elements other than hydrogen and oxygen. Hydrogen and oxygen must be balanced in the end.