Question

Identify the balanced chemical reaction of sodium chloride and sulphuric acid:
A.\[2{\text{NaCl}} + {{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4} + 2{\text{HCl}}\]
B.\[2{\text{NaCl}} + {{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to 2{\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4} + 2{\text{HCl}}\]
C.\[2{\text{NaCl}} + 2{{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4} + 2{\text{HCl}}\]
D.\[2{\text{NaCl}} + {{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to 2{\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4} + 3{\text{HCl}}\]

Answer 1

Hint: For the above question we must have the knowledge of balancing the chemical equation. The above reaction is a double decomposition reaction. The reaction will be balanced when each element on both sides has the same number of atoms.

Complete step by step answer:
To balance a chemical equation all we need to equate the number of atoms of each of the elements in reactants with that of the product. We need to use hit and trial methods in these cases. Let us check in each of the above options.
\[2{\text{NaCl}} + {{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4} + 2{\text{HCl}}\]
In the above equation, we have 2 sodium atoms on the left hand side and 2 sodium atoms on right hand sides, so sodium atoms are balanced. Now on the left hand side there are 2 chlorine atoms and on the right hand side there are 2 chlorine atoms. Similarly there are 2 hydrogen atoms, 4 oxygen atoms and 1 sulphur atom on the reactant side and the same on the product side. So the above chemical equation is balanced.
\[2{\text{NaCl}} + {{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to 2{\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4} + 2{\text{HCl}}\]
In the above equation, we have 2 sodium atoms on the left hand side but 4 sodium atoms on right hand sides, so sodium atoms are not balanced. Even if one element is not balanced then the equation is said to be unbalanced.
\[2{\text{NaCl}} + 2{{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4} + 2{\text{HCl}}\]
In the above equation, we have 2 sodium atoms on right hand side and 2 sodium atoms on right hand sides, so sodium atoms are balanced. Now on the right hand side there are 2 chlorine atoms and on the left hand side there are 2 chlorine atoms. There are 4 hydrogen atoms and one reactant side and 2 hydrogen atoms. So the above chemical equation is unbalanced.
\[2{\text{NaCl}} + {{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to 2{\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4} + 3{\text{HCl}}\]
In the above equation too, we have 2 sodium atoms on the left hand side but 4 sodium atoms on the right hand side, so sodium atoms are not balanced. The equation is said to be unbalanced.

Hence the correct option is A.

Note:
It is necessary to balance a chemical equation because to be practically feasible, they must follow law of constant proportion and law of conservation of mass. These laws will be obeyed if we balance the reaction otherwise total mass of reactant and product will vary which is not possible.