Question

\[{\text{aHgS}} + {\text{bHCl}} + {\text{cHN}}{{\text{O}}_3} \to {\text{d}}{{\text{H}}_2} + {\text{HgC}}{{\text{l}}_4} + {\text{eNO}} + {\text{f S}} + {\text{g}}{{\text{H}}_2}{\text{O}}\]
The value of b, c, e and g are respectively.
A.\[2,2,4,12\]
B.\[6,1,1,2\]
C.\[12,2,2,4\]
D.Both B and C

Answer 1

Hint: For the above question we must have the knowledge of balancing the chemical equation. Balance the above chemical equation to get the value of required coefficients. For balancing equation number of atoms of each element should be equal.

Complete step by step solution:
To balance a chemical equation all we need to equate the number of atoms of each of the element in reactants with that of product. We need to use hit and trail method in these cases. Initially we consider the following equation:
\[{\text{aHgS}} + {\text{bHCl}} + {\text{cHN}}{{\text{O}}_3} \to {\text{d}}{{\text{H}}_2} + {\text{HgC}}{{\text{l}}_4} + {\text{eNO}} + {\text{f S}} + {\text{g}}{{\text{H}}_2}{\text{O}}\]
Let us fist equate number of hydrogen. Since there are 4 chlorine atoms on RHS hence we can only use multiples of 4 as b because otherwise chlorine won’t balance. Let us consider b equals to 12, we will get to know why we choose 12 only and not 8. And hence we have to add 3 on product side to balance the number of chlorine atoms. We need to add even number in place of c because on the product side hydrogen is even. Let us add 2 as c, the equation will be:
\[{\text{aHgS}} + 12{\text{HCl}} + 2{\text{HN}}{{\text{O}}_3} \to 3{{\text{H}}_2} + 3{\text{HgC}}{{\text{l}}_4} + {\text{eNO}} + {\text{f S}} + 4{{\text{H}}_2}{\text{O}}\]
Now to balance number of nitrogen we need to have e equal to 2. To balance \[{\text{Hg}}\]we will have to place ‘a’ equals to 3 and to balance \[{\text{S}}\]we need to add f equals to 3. The net equation will be:
\[{\text{3HgS}} + 12{\text{HCl}} + 2{\text{HN}}{{\text{O}}_3} \to 3{{\text{H}}_2} + 3{\text{HgC}}{{\text{l}}_4} + 2{\text{NO}} + 3{\text{S}} + 4{{\text{H}}_2}{\text{O}}\]
Comparing the required coefficient we will see that option C is correct.

Note: It is necessary to balance a chemical equation because the chemical equation 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.