Question

In the balanced equation, \[{H_2}S{O_4} + xHI \to {H_2}S + y{I_2} + z{H_2}O\] , the values of $x,y$ and $z$ are respectively:
A.$x = 3,y = 5,z = 2$
B.$x = 4,y = 8,z = 5$
C.$x = 8,y = 4,z = 4$
D.$x = 5,y = 3,z = 1$

Answer 1

Hint:To find the values of $x,y$ and $z$ we have to balance the equation. The coefficients of hydrogen iodide, iodine and water in the balanced chemical equation will be the values of $x,y$ and $z$ respectively.

Complete step by step answer:
Balanced chemical equation: It is defined as the reaction in which the number of atoms on both the sides i.e. on the reactant side and on the product side is the same.
Here in the given equation if we have to find the values of $x,y$ and $z$ then we have the balance of the reaction. Sulphuric acid and hydrogen iodide are the reactants and hydrogen sulphide, iodine and water are as products formed.
The coefficients of hydrogen iodide, iodine and water in the balanced chemical equation will be the values of $x,y$ and $z$ respectively.
Steps to balance the chemical reactions are as follows:
Step (i) First balance the atoms other than hydrogen and oxygen. In the given reaction atoms other than hydrogen and oxygen are sulphur and iodine. The number of sulphur atoms on both of the sides is one i.e. balanced and the number of iodine on reactant side is one and on product side is two. So to balance the number of iodine atoms, multiply the hydrogen iodide with two. So the reaction will become as: \[{H_2}S{O_4} + 2HI \to {H_2}S + y{I_2} + z{H_2}O\].
Step (ii) Now balance the number of oxygen atoms. Here the number of oxygen on the reactant side after the first step is four and on the product side is one. So multiply the water which contains the oxygen atoms with four. Now the number of oxygen atoms is balanced i.e. four. So the equation will be as:
\[{H_2}S{O_4} + 2HI \to {H_2}S + y{I_2} + 4{H_2}O\]
Step (iii) Now balance the number of hydrogen atoms. Here the number of hydrogen on the reactant side after the first step is six and on the product side ten. So to balance it multiply the hydrogen iodide with four. Now the number of hydrogen atoms on both sides are the same i.e. ten. So the equation will be as:
\[{H_2}S{O_4} + 8HI \to {H_2}S + y{I_2} + 4{H_2}O\]
Step (iv) But now the numbers of iodine are not balanced so to balance the number of iodine atoms multiply the iodine on the product side by four. Now the number of iodine atoms on both sides are the same i.e. eight. The reaction is as:
\[{H_2}S{O_4} + 8HI \to {H_2}S + 4{I_2} + 4{H_2}O\]
Now the whole reaction is balanced i.e. the number of hydrogen atoms are ten, sulphur atoms are one, oxygen atoms are four and iodine atoms are eight on both the sides.
So the values of $x,y$ and $z$ are $8,4$ and $4$ respectively.
Hence option C is correct.

Note: There are many methods to balance the chemical reaction. The method used in the above question is one. Another way to balance the chemical reaction can be by using oxidation number. First find the oxidation number of each atom on the reactant and product side. Then find the change in oxidation number then multiply that molecule with that change to get the balanced reaction.