# How many liters of carbon dioxide are produced when 2.0 moles of CH_4 are burned at STP?

Assuming combustion to be the reaction producing the $C {O}_{2}$, you need to first write the balanced equation. Then you can calculate how much $C {O}_{2}$ 2.0 moles of methane would produce with complete reaction.
CH_4 + 2O_2 → CO_2 + 2H_2O