chemistry-balancing an equation?

It's easy, really. You just have to make sure you have the same thing on both sides.

An easy example, precipitation of silver chloride:

NaCl + AgNO3 -> NaNO3 + AgCl

On the left we have 1 Na, 1 Cl, 1Ag, and 1 NO3

On the right we have 1 Na, 1 NO3 1AG and 1 Cl

It's the same, so we don't need to do anything.

A hard one: burning petrol

The basic equation:

C8H10 + O2 -> CO2 + H2O

On the left we have 8 C's, but we only have one on the right, also we have 10 H's on the left, and only 2 on the right so we make it:

C8H10 +O2 -> 8CO2 + 5H2O

Now we have 21 O's on the right, but only 2 on the left:

C8H10 + 10 1/2O2 -> 8CO2 + 5H2O

In the olden days you could leave it like this, but these days the convention is to double them all so you get whole numbers:

2C8H10 + 21O2 -> 16CO2 + 10H20

:)

lol im in yar 10 and were doing that in my chem & phys class. the teacher we had said it was just a matter of trial and error. alsoo said something to do with starting with the one that are closest together