Balance the following equations;

a) CH4(g) + O2(g) --heat--> CO2(g) + H2O(g)


This equation appears to be a little more complicated that the formation equations we were discussing. But if maintain control we'll see these are not that difficult. It is all in the approach.

To balance combustion reactions always balance the element oxygen, O2, last. If we do that we need to balance carbon and hydrogen first, we'll do that beginning with carbon.

CH4(g) + O2(g) --heat--> CO2(g) + H2O(g)

There is one carbon atom on both sides so that was easy!

Now hydrogen...let's see four hydrogen atoms on the left (CH4) and only two on the right (H2O). So I'll need to change the coefficient before H2O from '1' to '2' and that will balance the hydrogen atoms.

CH4(g) + O2(g) --heat--> CO2(g) + 2H2O(g)

Now we'll balance the oxygen atoms. There are two oxygen atoms (O2) on the left and four oxygen atoms on the right (CO2 + 2H2O). So I'll need to change the coefficient from a '1' to a '2' in front of O2.

CH4(g) + 2O2(g) --heat--> CO2(g) + 2H2O(g)

Now the equation is balanced.