Basic Chemistry Help

[which doctor]

I am working on some chem homework and I understand it all except a few problems. They have to do with balancing equations so that each side equals out the others.

Note that the numbers in bold are supposed to be subscripts.

__C3H6 + __O2 ----> __CO2 + __H2O

The goal is to make sure there are the same number of each element on both the reactants side and the products side.

You need to fill in the blank with a coefficient.

Good luck!

[Tormented by Treachery]

If you're asking for help, then here we go, but if not, then I will feel stupid :).

To start, you find the one element that only appears once on either side of the equation, in this case, C. The lowest common multiple they have is 3, so you mutliply each of the compounds to equal 3 C's on each side. Thus, we now have:

C3H6 + __O2 ----> 3CO2 + __H2O

Because the original compound, C3H6 has no coefficient, there are 6 H's. This means that the right side of the equation must have the same amount, so we multiply again to achieve this:

C3H6 + __O2 ----> 3CO2 + 3 H2O

Here is where we encounter a problem. With the O2 on the left, there can only be multiples of 2. This means that the 3 O's in H2O must be doubled, yielding 6. To correct the amount of H's, this means we must return to our original 2 compounds and double those as well:

2 C3H6 + __O2 ----> 6 CO2 + 6 H2O

Now that we have all except one coefficient squared away, we must add up all of the O's on the right side. with the 12 coming from CO2 and 6 more from H2O, that adds up to 18 total O's. Because the compound O2 is diatomic (that is, it occurs naturally paired up to fill outer electron layers), you need to divide 18 by 2, which equals 9. Thus, we know the last coefficient, and the equation reads:

2 C3H6 + 9 O2 ----> 6 CO2 + 6 H2O

[which doctor]

You did exactly what I wanted someone to do, thanks a lot. Since this worked out so well I might just ask all my chemistry questions in this topic.

[Tormented by Treachery]

Sounds great, glad to be of help :).