What volume of carbon dioxide is produced when 7.5g of butane react with 19g of oxygen gas at 74 degrees celsius at 550 torr?
2C4H10 + 13O2 ==> 8CO2 + 10H2O
This is a limiting reagent (LR) problem.
mols C4H10 = grams/molar mass = ?
mols O2 = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols C4H10 to mols CO2.'
Do the same for mols O2 to mols CO2.
It is likely that these two values will not agree; in LR problems the correct answer is ALWAYS the smaller value and the reagent responsible for that value is the LR.
Now use the smaller value for mols and plug the appropriate conditions of the problem into PV = nRT and solve for volume.