If 5.0 liters of carbon dioxide gas are produced by the reaction below at 273 k and 1.00 atm, how many liters of oxygen gas were used in the reaction?

The balanced chemical reaction was not given. I will just assume an organic compound for this case. The balanced reaction would be:

C6H6 + 15/2O2 = 6CO2 + 3H2O

We are given the amount of carbon dioxide gas produced from the reaction. This will be the starting point of our calculation. We use the ideal gas equation to find for the number of moles.

n = PV / RT = 1.00(5L) / (0.08206 atm L/mol K ) 273 K
n= 0.2232 mol CO2

0.2232 mol CO2 (15/2 mol O2 / 6 mol CO2) ( 14.03 g CO2 / 1 mol CO2 ) = 3.9144 mol O2

V = nRT/P = 3.9144 mol O2 x 273 K x 0.08206 atm L/mol K / 1 atm
V=87.6912 L