Question

Whats an easy way on remembering how balance equations?

Answer 1

Save the Hydrogens and Oxygens for last and do everything else first. Think of it like math too.
For instance:
Fe + S --> FeS2
there aren't any hygrogens or oxygens, so don't worry about that. But check for both sides.
Do each one at a time
There's one Fe on the left, and one Fe on the right. So you're good thus far.
Now S. You have one on the left, but two on the right, so then put a 2 in front of the S on the left side to make it look like this:
Fe + 2S --> FeS2

Now here's a harder one:
PCl3 + H2O --> H3PO3 + HCl
Now we have both H and O, so save those for last.
Lets start with P. We have one on the left and one on the right. We're good.
Now Cl. We have 3 on the left and one on the right. No biggie, just put it in front of the HCl on the left to look like this:
PCl3 +H2O --> H3PO3 + 3HCl
Ok, lets get into Hydrogens now. We have 2 on the left and 6 on the right (remember because we added a 3 in front of HCl)
Since there's already a 2 in there, we just need to figure out what to multiply it by to get to 6, which would be 3. So now it looks like this:
PCl3 + 3H2O --> H3PO3 + 3HCl
Ok, last we have our Oxygens. count 'em up, we have 3 on the left (because we have 3H2O now that carries over to the O, making 3 O) and 3 on the right side. We're done!
Finished looks like this:
PCl3 + 3H2O --> H3PO3 + 3HCl

I know it isn't that short, but it's good to see it played out and applied. Really the key is practice but in sum, some quick tips are:
-Save Hydrogens and Oxygens till very last
-Think in math terms (that the numbers carry)

To check your answers, plug it the unbalanced equation into this site:
http://www.webqc.org/balance.php