Summary Class 10 chemistry chapter 1 notes CBSE

Balanced Chemical Equations

In the reaction Mg + O​2​ → MgO, the number of atoms of each
element on either side of the arrow is not equal. Therefore, this is an
unbalanced ​chemical equation​. Then what is a balanced equation?
Let’s find out below and learn how to balance a chemical equation.


Balanced Equations

As you have already learned earlier, ​mass can neither be created nor
destroyed​. This law applies to a chemical reaction too. This means that
the total mass of elements in the products of a chemical reaction has to
be equal to the total mass of the elements in the reactants. The number
of atoms of each element remains the same, before and after a
chemical reaction. For example, let’s look at the following chemical
equation –


Zinc + Sulphuric acid → Zinc sulfate + Hydrogen


This is further simplified as –


Zn + H​2​SO​4​ → ZnSO​4​ + H​2

,Now, let us look at the number of ​atoms​ of each element on LHS and
RHS –


Number of atoms in Number of atoms in
Element
reactants (LHS) products (RHS)




Zn 1 1




H 2 2




S 1 1




O 4 4




As you can see, the number of atoms of each element on LHS and
RHS are the same. Therefore, this chemical equation is a ‘balanced
equation’. Now, look at the following equation –


Fe +H​2​O → Fe​3​O​4​ +H​2

, If you notice, the number of atoms of each element are not the same
on both sides of the arrow. Therefore, this is an ‘unbalanced’ equation.
We can balance this equation using the following steps –


Step I

First, draw boxes around each formula without changing anything
inside the boxes.




Step II

List the number of atoms of each element on either side of the arrow
in the equation –


Number of atoms in Number of atoms in
Element
reactants (LHS) products (RHS)




Fe 1 3




H 2 2