CH4+2O2 gives 2H2O+CO2
so for every mole of ch4 we produce 1 mole co2
since the molecular weight of ch4 is 16 we can divide 50.6 by 16 to find the number of moles for ch4 which is 3.16. we already know for each mole of ch4 we have one mole of co2. so for 3.16 mole of ch4 we produce 3.16 mole of co2. 1 mole of co2 is 44gram. so 3.16 mole would be 139.15 gram.