The mass of a non-volatile solute (molecular mass = 40) which should be dissolved in 114 g octane to — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

Octane ($C_8H_{18}$) molar mass = 114 g/mol. Moles of octane $N = 114/114 = 1$ mol. Relative lowering: $(P^\circ - P) / P = n / N \implies (100 - 80)/80 = n / 1 \implies 0.25 = n$. Mass of solute $= n \times M = 0.25 \times 40 = 10$ g. Therefore, correct answer is D.