Balancing Equation

What is a balanced equation?

A chemical equation is balanced when the number of atoms of each type on each side of the equation is the same. Which means if you have 12 hydrogens on the left hand side of the equation, you must have 12 hydrogens on the right hand side, if there are 4 oxygens on the left, there must 4 oxygens on the right, and so on. This is because of the law of conservation of mass - you can't make or destroy atoms during a chemical reaction. But you can't just add atoms at random to each side, you have to work with the molecules of the reactants. Also, you will find it very tricky to try to balance a word equation, it is very much easier to use a chemical equation with chemical symbols, as then you will be able to see how many atoms of each type are in each chemical.

Example 1:

Unbalanced Equation:- C₃H₈ + O₂ ---> H₂O + CO₂

-There are three carbons on the left, but only one on the right.
-There are eight hydrogens on the left but only two on the right.
-There are two oxygens on the left but three on the right.


Balanced Equation:- C₃H₈ + 5O₂ ---> 4H₂O + 3CO₂

Example 2:

Unbalanced equation:- H₂SO₄ + Fe ---> Fe₂(SO₄)₃ + H₂

-Balance the SO₄ first (as it is a complex ion and it is in one chemcial species on each side)
3H₂SO₄ + Fe ---> Fe₂(SO₄)₃ + H₂

-Now balance the Fe (which is also in one chemical on each side)
3H₂SO₄ + 2Fe ---> Fe₂(SO₄)₃ + H₂
-Finally, balance the hydrogen (although it is in one chemical species on each      side, it is usually a good idea to leave it until last)

Balanced Equation:- 3H₂SO₄ + 2Fe ---> Fe₂(SO₄)₃ + 3H₂