Question

\[{C_6}{H_6}\left( g \right) + {O_2}\left( g \right) \to C{O_2}\left( g \right) + {H_2}O\left( g \right)\]
When the equation for the reaction represented above is balanced and all the coefficients is reduced to lowest whole number terms , the coefficient for ${H_2}O\left( g \right)$ is :
$\left( A \right)2$
$\left( B \right)3$
$\left( C \right)4$
$\left( D \right)5$
$\left( E \right)6$

Answer 1

Hint: First balance the equation. To balance the equation you need to check that each element present has the same number in both the reactants and products. You cannot change the subscript of the reactions you just need to focus on the coefficient .

Complete step by step answer:
In a chemical reaction there are two types of numbers present . one is the subscript and another one is the coefficient. Subscript is a part of a formula and it can't be changed whereas coefficient is the number of particular reactants present .
 \[{C_6}{H_6}\left( g \right) + {O_2}\left( g \right) \to C{O_2}\left( g \right) + {H_2}O\left( g \right)\]
In this reaction we need to balance it .
- $1.$ First let us calculate the number of hydrogen
We can see the number is different in reactant. We have 6 hydrogen in the reactant and 2 hydrogen in the product , for making it equal we need to add 6 in the water molecule and 2 in the benzene , then it will become equal .
\[2{C_6}{H_6}\left( g \right) + {O_2}\left( g \right) \to C{O_2}\left( g \right) + 6{H_2}O\left( g \right)\]

- $2.$ Now we need to check the number of carbon
We need to add 12 in the carbon dioxide to make both sides equal .
\[2{C_6}{H_6}\left( g \right) + {O_2}\left( g \right) \to 12C{O_2}\left( g \right) + 6{H_2}O\left( g \right)\]

- $3.$ Now lastly equal the number of oxygen
 We have to add 15 in the oxygen molecule which is reactant for making same number both the side
\[2{C_6}{H_6}\left( g \right) + 15{O_2}\left( g \right) \to 12C{O_2}\left( g \right) + 6{H_2}O\left( g \right)\]
- Now the above equation has become balanced.
So , after balancing we can say that the coefficient of ${H_2}O\left( g \right)$ is $6$
The correct option is option “E” .

Note: In a chemical reaction just like energy , the atoms can neither be created nor destroyed . so even if the reactions are changed the number of the atoms in the reactant and product will always be equal .