One mole of heptane (V.P. = ) is mixed with four moles of octane (V.P. = ) to form an ideal solution — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

Total moles $= 1 + 4 = 5$. Mole fraction of heptane $= 1/5$, and octane $= 4/5$. By Raoult's law, $P_{total} = P_{heptane}^0 X_{heptane} + P_{octane}^0 X_{octane} = (92 \times \frac{1}{5}) + (31 \times \frac{4}{5}) = 18.4 + 24.8 = 43.2\text{ mm Hg}$.