45 grams of octane react with oxygen in the air. How many moles of oxygen were consumed in the reaction?

Answer 1

octane = C₈H₁₈

oxygen = O₂

2 C₈H₁₈ + 25 O₂ ==> 16 CO2 + 18 H2O .. balanced equation

molar mass C₈H₁₈ = 114 g / mol

mols C₈H₁₈ present = 45 g x 1 mol / 114 g = 0.3947 mols

mols O₂ consumed = 0.3947 mol C₈H₁₈ x 25 mol O₂ / 2 mol C₈H₁₈ = 4.9 moles O₂ consumed (2 sig.figs)