What are the 18 octane isomers?

After the reaction, how much octane is left?

• 2 C8H18 + 25 O2 --> 16 CO2 + 18 H20 .208mol of octane is allowed to react with .780 mol of oxygen. Oxygen is the limiting reactant. After the reaction, how much octane is left?

• Answer:

  Chantel, You are totally correct that oxygen is the limiting reagent: for every 25 moles of oxygen, you use up two moles of octane. That means for 0.780 moles of oxygen, you use up 0.708 x 2/25 moles of oxygen = 0.0566 moles of octane. Subtract that amount from 0.208 moles of octane, and you get 0.208 - [0.708 x (25/2)] = 0.151 moles of octane left. If you need to give the number of grams, multiply that number by the molecular weight of octane, 114.23: 114.23 x 0.151 = 17.3 grams. Hope this helped!