Question

Some chemical equations are given below.
$\begin{align}
  & C+{{O}_{2}}\to C{{O}_{2}} \\
 & C{{H}_{4}}+2{{O}_{2}}\to C{{O}_{2}}+2{{H}_{2}}O \\
 & {{N}_{2}}+{{O}_{2}}\to NO \\
 & CaC{{O}_{2}}\to CaO+C{{O}_{2}} \\
 & {{H}_{2}}+{{I}_{2}}\to HI \\
 & Fe+HCl\to FeC{{l}_{2}}+{{H}_{2}} \\
 & C{{O}_{2}}+C\to CO \\
\end{align}$
Balance the unbalanced equations.

Answer 1

Hint: A balanced chemical equation shows the exact number of atoms on the reactants and that of the products side. There are various types of reactions in which either the reactants combine, decompose, or displace atoms to form new products. The balancing will require writing the same number of moles of reactants and products by a hit and trial method.

Complete answer:
We have been given various equations of chemical reactions. We have to find the unbalanced equations and balance them. An unbalanced equation will consist of an unequal number of the atoms in the compounds on the reactants and the products side. While a balanced chemical equation will have the same amount of atoms in reactants and the products.
Among the given equations, the balanced equations having same number of atoms and moles of reactants and products are:
$\begin{align}
  & C+{{O}_{2}}\to C{{O}_{2}} \\
 & C{{H}_{4}}+2{{O}_{2}}\to C{{O}_{2}}+2{{H}_{2}}O \\
 & CaC{{O}_{2}}\to CaO+C{{O}_{2}} \\
\end{align}$
Now, we have to balance the remaining equations. This is done by a hit and trial method. A chemical equation is balanced by balancing the charges on the atoms that form a molecule; the charges should be the same at the reactant as well as the product's side. Then by equalizing the charges, the number of atoms is increased by adding simple whole number coefficients. Therefore the balanced equations will be:
$\begin{align}
  & {{N}_{2}}+{{O}_{2}}\to 2NO \\
 & {{H}_{2}}+{{I}_{2}}\to 2HI \\
 & Fe+2HCl\to FeC{{l}_{2}}+{{H}_{2}} \\
 & C{{O}_{2}}+C\to 2CO \\
\end{align}$
In these equations, the number of reactant atoms and that of products are balanced by balancing the charges.
Hence, the unbalanced equations are balanced.

Note:
The balancing is done by taking into account the valency of individual atoms. For example, $C{{O}_{2}}+C\to CO$ is unbalanced as the charge on carbon is +4 and that on oxygen is -2. So, in the reactants side the total carbon atoms are 2 having +4 charges but in products they are 1 carbon having +4, and oxygen is 2 on reactant and 1 on product side, therefore 2 is added on product CO that balances the charges as well as the number of atoms.