# Physical Chemistry (dissolution of a substance)

## Homework Statement

The dissolution of 5.25 g of a substance in 565 g of benzene at 298 K raises the boiling
point by 0.625°C. Note that Kf = 5.12 K kg mol-1, and Kb = 2.53 K kg mol-1, and the density of benzene is 876.6 kg m-3. Calculate the freezing point depression, the ratio of the vapor pressure above the solution to that of the pure solvent, the osmotic pressure,
and the molecular weight of the solute.

Pressure benzene= 103Torr at 298 K

## Homework Equations

$$\Delta$$T=Kfb (freezing point depression)

## The Attempt at a Solution

For the first part I'm assuming I need to find Delta T and that is the freezing point depression but do not know how to figure out the molality (b) of the unknown substance. I know it is moles of solute per kilograms solvent but dont know how to determine the number of moles.