Given the equation 2C8H18 + 25O2 = 16 CO2 + 18H2O: How many moles of oxygen gas (O2) are consumed upon combustion of 2.20 L of octane ( D = 0.703 g/mL)?

Answer 1

well, since all the compounds are gases, you can use the law of volumes to surmise
2*1.1 liters octane
25*1.1 liters oxygen
16*1.1 liters carbon dioxide
18*1.1 liters water vapor.
So moles of O2? it will be (25*1.1)/22.4 moles O2. No need to worry about temp, pressure, because all the gases are at same temp, pressure.

Answer 2

yes