C3H8 + 5O2 --> 3CO2 + 4H2O.................. (12)

Step 4: Check the answer. Count the numbers and kinds of atoms on both sides of the equation to make sure they are the same.

Eg-2: Iron oxide reacts with Aluminum to form iron and Aluminum trioxide. Write the chemical equation to show the reaction and balance it.

Step 1: Write the equation using the correct chemical symbols and formulae for all the reactants and products.

Fe2O3 + Al --> Fe + Al2sub>O3.................. (13)

Step 2: Find the suitable coefficient for the reactants and products, to equate the number of atoms of each element on both sides.

i. Examine the number of atoms of each element present in equation (13) on both sides.

1

In the above equation (13), Number of oxygen atoms is equal on both sides. We have to balance the remaining atoms.



ii.There are 2 Fe atoms on left side(on reactant side). There is one Fe atom on right side(on products side). To equate number of Fe atoms, multiply Fe by 2 on product side.

Now the partially balanced equation is:

Fe2O3 + Al --> 2Fe + Al2O3.................. (14)

iii. In the above equation(14) number of Aluminum atoms still unbalanced.

There is one ‘Al’ atom on left side and 2 ‘Al’ atoms on the right side (in Al2O3), to balance ‘Al’ atoms on both sides multiply ‘Al’ by 2 on left side of arrow mark.

Now the partially balanced equation:
Fe2O3 + 2Al --> 2Fe + Al2O3 ................ (15)

The above equation(15), the number of atoms of each element is same on both sides of arrow mark. This is a balanced chemical equation.

Step 3: The above equation(15) is balanced and coefficients are also smallest whole numbers.

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