How to do balancing equations

It's quite hard to explain without an example, but I'll give it a go:

Basically, you have to count the number of an element on one side of the equation, then count it on the other, and the aim of balancing the equation is to get the 2 values to be the same (as mass cannot be created or destroyed).

This involves multiplication of the molecule (s) on either side of the equation in order to balance the whole thing. Note this is not like maths, you dont have to do the same to both sides, but you do have to multiply out entire molecules - you cannot multiply just the H2 in H2O for example.

A reasonably basic example of this balancing is:

Fe + Cl2 = FeCl3

The first thing I notice is that there is an even number of Cl atoms on the left, and an odd number on the right, so the first thing I'll do is multiply the one on the right to get it to an even number, ie by 2.

Fe + Cl2 = 2 (FeCl3)

Expanding that gives Fe2Cl6 (although you dont write it like that). So we need to get 6 Cl atoms and 2 Fe atoms by multiplying the left hand molecules by amounts if possible. If you look at that, we can achieve that, by multiplying Cl2 by 3, and Fe by 2.

2Fe + 3Cl2 = 2FeCl3

And there you have your balanced equation, you'll notice that the number of any given element has the same number of atoms on both sides of the equation.