Question

A chemical equation is balanced when ________. a the sum of the coefficients of the reactants is equal to the sum of the coefficients of the products b the charge on each atom is the same in both the reactants and products c the number of atoms of each element is the same in both the reactants and products

Answer 1

The correct answer is C ) the number of atoms of each element is the same in both the reactants and products.

For example this equation the combustion of methane CH4:

CH4 + O2 → CO2 +H2O

this is not balanced equation:

as we have the no.of C atoms on the right side = the atoms on the left side = 1 
but the no.of H atoms on the right side = 2 
and no.of H atoms on the left side = 4 

so to get the balanced equation we have to make no.of atoms equal on both sides:

So, we put 2H2O instead of H2O

CH4 + O2 → CO2  +  2H2O

now the no of O atoms on the right side = 4 
and the no.of  O atoms on the left side = 2 

so, we put 2O2 instead of O2 to make no.of O atoms equal on both sides 

So we finally get the balanced equation:

CH4 + 2O2 → CO2 + 2H2O

-have 1 C atom on both sides
-have 4 H atoms on both sides
-Have 4 O atoms on both sides

So the equation will be balanced when no.of atoms of each element are the same in both the reactants and products