2 C8H18 + 25 O2 → 16 CO2 + 18 H2O

From the balanced chemical equation, we can see that 2 moles of octane react with 25 moles of oxygen. Therefore, to burn 1.50 moles of octane, we need:

(1.50 mol C8H18) × (25 mol O2 / 2 mol C8H18) = 18.75 mol O2

Therefore, 18.75 moles of O2 are needed to burn 1.50 moles of C8H18.