Chemical equations must be balanced to obey the law of conservation of mass. This law states that matter is neither created nor destroyed in a chemical reaction, only transformed. To balance an equation, one counts the number of atoms of each element on both sides of the reaction. If the numbers are not equal, coefficients are placed in front of formulas to balance the atoms. For example, the equation H2 + Cl2 → HCl is balanced by adding a coefficient of 2 in front of HCl to make the chlorine atoms equal on both sides of the reaction. Balancing chemical equations ensures the law of conservation of mass is followed.

1. THE LANGUAGE OF
CHEMISTRY
- Balancing chemical equations

2. CHEMICAL EQUATIONS –
NEED FOR BALANCING
Law of conservation of mass states that
matter can neither be created nor be
destroyed ,only it can be transformed from
one form to another
To obey the law of conservation of mass

3. LAW OF CONSERVATION OF MASS -
EXPLANATION

4. LAW OF CONSERVATION OF MASS -
EXPLANATION
In a chemical reaction ,
Total mass of Total mass of
reactants products
i.e ., the mass is conserved

5. HOW TO BALANCE
A CHEMICAL EQUATION ?
Step 1 :Count the number of atoms of each
element on reactant and product side(if they
are equal ,then step 2 is not necessary)
Step 2 :Start balancing with the compound
that contains the maximum number of atoms
(by changing the coefficients)

6. WHILE BALANCING
A CHEMICAL EQUATION …
 A coefficient is an integer that is placed in
front of the chemical formula

7. BALANCING CHEMICAL EQUATIONS
Balance the following chemical equation:
H2 + Cl2 → HCl
Reactants No. of atoms Products No. of atoms
H2 H = 2 HCl H = 1
Cl2 Cl = 2 Cl = 1
Step 1: Count the no.of atoms in reactants
and products
The number of hydrogen and chlorine
atoms are not balanced !

8. BALANCING CHEMICAL EQUATIONS
H2 + Cl2 → 2HCl
Reactants No.of atoms Products No.of atoms
H2 H = 2 2 HCl H = 2
Cl2 Cl = 2 Cl = 2
Step 2: Balance the number of chlorine atoms
by adding the coefficient of 2 in front of HCl
and count the number of atoms again.
The equation is balanced !

9. UPCOMING TOPICS…
- Balancing chemical equations:
Examples