Learn How to Balance Chemical Equation

Step by Step Procedure for Balancing Chemical Equation

What is a chemical equation?

It is defined as the representation of reactions taking place between chemicals, with the reactants on the left hand side (L.H.S) and the product obtained from the reaction on the right hand side (R.H.S)

When is an equation called balanced / Unbalanced?

An equation is said to be balanced when there are equal number of molecules for each elements on both sides of the equations.

Example:
2Na + Cl2 -> 2NaCl

In the above equation we have, 2 Sodium (Na) and 2 Chlorine (Cl) on both L.H.S and R.H.S, Hence the equation is said to be balanced. llly, an equation is said to be unbalanced when the number of molecules for each elements are not equal on both sides.

Example:
H2 + O2 -> H2O

Considering the equation above, we have 2 hydrogen (H) and 2 oxygen (O) on the L.H.S and 2 hydrogen (H) and only 1 oxygen (O) on the R.H.S. Hence with the unequal number of oxygen molecules the chemical equation is said to be unbalanced.

How to balance an unbalanced chemical equation?

Let us learn here how to balance the above unbalanced equation with step by step procedure.

Given,
H2 + O2 -> H2O

To balance this the unbalanced oxygen molecules, we add 2 in front of the product on R.H.S. We get,

H2 + O2 -> (2) H2O

Now, we have 2 Oxygen's but 4 Hydrogen's on the R.H.S. In order to balance the same, we add an another 2 in front of Hydrogen on the L.H.S

(2) H2 + O2 -> (2) H2O

Now, the equation is balanced with 4 Hydrogen's (H) and 4 Oxygen's on both sides.

Let us try the same with another example.

Consider the equation,

KMnO4 + HCl = KCl + MnCl2 + H2O + Cl2

First table the number of elements on each side to know the imbalance.

ElementsOn L.H.SOn R.H.S
K11
Mn11
O41
H12
Cl15

From the table we get that, K and Mn are balanced and the elements O, H and Cl are not balanced. First, let us consider balancing Hydrogen molecule (H) as it is required to bring only 1 time on the L.H.S. To balance H we need to add 2 in front of HCL on the L.H.S Now, the equation becomes

KMnO4 + (2) HCl = KCl + MnCl2 + H2O + Cl2

Now, again table the elements,

ElementsOn L.H.SOn R.H.S
K11
Mn11
O41
H22
Cl25

We get, K, MN and H are balanced while O and Cl are still unbalanced.

Next, let us balance of Oxygen (O). We now have 4 Oxygen's on the L.H.S and 1 on the R.H.S

To balance 'O', we can add 4 in front of water molecule (H2O) on the R.H.S

Now, the equation becomes

KMnO4 + (2) HCl = KCl + MnCl2 + (4) H2O + Cl2

by tabling the elements again,

ElementsOn L.H.SOn R.H.S
K11
Mn11
O44
H28
Cl25

Now, balance for Cl and H by adding +3 on L.H.S

KMnO4 + (2+3) HCl = KCl + MnCl2 + (4) H2O + Cl2
KMnO4 + (5) HCl = KCl + MnCl2 + (4) H2O + Cl2

Table the elements,

ElementsOn L.H.SOn R.H.S
K11
Mn11
O44
H58
Cl55

To balance H, add +2 to HCl on R.H.S we get,

KMnO4 + (6+2) HCl = KCl + MnCl2 + (4) H2O + Cl2
KMnO4 + (8) HCl = KCl + MnCl2 + (4) H2O + Cl2

Table the elements,

ElementsOn L.H.SOn R.H.S
K11
Mn11
O44
H88
Cl85

llly try to balance the number of molecules on both sides of the formula to balance the equation.

KMnO4 + (8) HCl = KCl + MnCl2 + (4) H2O + Cl2
KMnO4 + (8) HCl = KCl + MnCl2 + (4) H2O + (2) Cl2

Table the elements,

ElementsOn L.H.SOn R.H.S
K11
Mn11
O44
H88
Cl87

Now to balance Cl add 2 to KCL on R.H.S

KMnO4 + (8) HCl = (2) KCl + MnCl2 + (4) H2O + (2) Cl2
KMnO4 + (8) HCl = (2) KCl + MnCl2 + (4) H2O + (2) Cl2

Table the elements

ElementsOn L.H.SOn R.H.S
K12
Mn11
O44
H88
Cl88

Now, to balance 'k'

(2) KMnO4 + (8) HCl = (2) KCl + MnCl2 + (4) H2O + (2) Cl2

Table the elements

ElementsOn L.H.SOn R.H.S
K22
Mn21
O84
H88
Cl88

Now to balance Mn and O, add numbers till the equation becomes balanced.

(2) KMnO4 + (8) HCl = (2) KCl + MnCl2 + (4) H2O + (2) Cl2
(2) KMnO4 + (8+2) HCl = (2) KCl + (2) MnCl2 + (4+1) H2O + (2) Cl2
(2) KMnO4 + (10) HCl = (2) KCl + (2) MnCl2 + (5) H2O + (2) Cl2

Table the elements

ElementsOn L.H.SOn R.H.S
K22
Mn22
O85
H1010
Cl1010

Now to balance 'O'

(2) KMnO4 + (10) HCl = (2) KCl + (2) MnCl2 + (5+3) H2O + (2) Cl2
(2) KMnO4 + (10) HCl = (2) KCl + (2) MnCl2 + (8) H2O + (2) Cl2
ElementsOn L.H.SOn R.H.S
K22
Mn22
O88
H1016
Cl1010

Now to balance 'H'

(2) KMnO4 + (10) HCl = (2) KCl + (2) MnCl2 + (8) H2O + (2) Cl2
(2) KMnO4 + (10+6) HCl = (2) KCl + (2) MnCl2 + (8) H2O + (2+3) Cl2
(2) KMnO4 + (16) HCl = (2) KCl + (2) MnCl2 + (8) H2O + (5) Cl2

Tabling the elements, We get,

ElementsOn L.H.SOn R.H.S
K22
Mn22
O88
H1616
Cl1616

Hence the balanced equation is,

2KMnO4 + 16HCl = 2KCl + 2MnCl2 + 8H2O + 5Cl2

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