Question

Balance the following equations by the oxidation number method.
$KI + {H_2}S{O_4} \to {K_2}S{O_4} + {I_2} + S{O_2} + {H_2}O$

Answer 1

Balance of the equation based on the law of conservation of mass and law of constant proportions. As we know that mass neither be created nor be destroyed. It is constant all the time. The chemical equation is balanced based on the number of atoms.

Complete step by step answer:
According to the question, Firstly look at the balance of the equation
Balance equation- When the number of an atom of the reactant and product is the same on both sides. Then, this reaction is called a balanced equation. It works according to the law of conservation of mass and the law of constant proportions.
Conservation of mass- It tells that the mass of a system is always constant, only energy changes from one form to another.
Constant proportions- It states that the element of a chemical compound always be in fixed mass. In this environment pure compounds are always in a fixed ratio of elements. For instance water, pure water always consists of fixed hydrogen and oxygen atoms.
Oxidation number method- In this method find the oxidation number of the element or track the electron and balance them.
$KI + {H_2}S{O_4} \to {K_2}S{O_4} + {I_2} + S{O_2} + {H_2}O$
Firstly, in this reaction, find the oxidation number of each.
$K$ - $+ 1$
$I$ - $- 1$
$H$ - $+ 1$ So, ${H_2}$ - $1*2 = 2$
$S$ - $+ 2 + x - 8 = 0 = 6$
$O$ - $- 2*4 \to - 8$
for ${K_2}S{O_4}$
$K$ - $1*2 = 2$
$O$ - $- 2*4 = - 8$
now find the $S$ oxidation number
$S$ - $+ 2 + x - 8 = 0 = 6$
for ${I_2}$
$I$ - $- 1*2 = - 2$
for $S{O_2}$
$O$ - $- 2*2 = - 4$
$S$ - $x - 4 = 0 = 4$
for ${H_2}O$
$H$ - $1*2 = 2$
$O$ - $- 2$
Now check if the oxidation number is increasing or decreasing from left to right side.
$K$ - increase by $1$
$I$ - decrease by $1$
$H$ - no change
$S$ - increase by $4$
$O$ - decrease by $6$
Now, check the charges. There are no charges on both side so, not to worry
Now, check the atoms on both sides, so write the equation
$KI + {H_2}S{O_4} \to {K_2}S{O_4} + {I_2} + S{O_2} + {H_2}O$
now balance the atom
$2KI + 2{H_2}S{O_4} \to {K_2}S{O_4} + {I_2} + S{O_2} + 2{H_2}O$
Here, we got a balanced equation.

Note:
In balancing chemical equations, Stoichiometric Coefficient involves, which is the total number of molecules participating in the chemical reaction. In chemical equations reactant and product denoted by their chemical formulas.