text: Well, I won't do it for you - but here is HOW to do it.  You have one C on each side so that is good.  But you have 4 Hs on the left side so you need 2 H2Os on the right to balance the Hs.  Now you have 4 Os on the right, so you need to make your 2 O2s on the left to balance the oxygen.\n\nCH4 + 2 O2   =   CO2 + 2 H2O\n\nNow - using the atomic weights of H=1, C=12, O=16, you get molecular weights for methane = 16 and 02 = 32.  Convert the weights of menthane and O2 into moles using the molecular wieghts - whichever is the smaller # of moles is the limiting reagent - meaning that the reaction will stop when this reagent has been used up.