The mass of a non-volatile solute of molar mass that should be dissolved in of octane to lower its vapour pressure by is:
Step 1: The mole fraction of non-volatile solute decreases proportionally to the relative decrease in vapour pressure.
Step 2: Applying formulae for mole fraction of non-volatile solute
The mass of a non-volatile solute of molar mass that should be dissolved in of octane to lower its vapor pressure by is .