What volume of oxygen at 25 degrees celsius and 93.5 kPa will use up 57.1 g of butane?
2C4H10 + 13O2 ==> 8CO2 + 10H2O
mols C4H10 = grams/molar mass
Using the coefficients in the balanced equation, convert mols C4H10 to mols O2.
Then use PV = nRT to solve for V. Note 93.5 kPa = 93.5/101.325 atm.
Don't forget to change T to kelvin.