the vapour pressure of ethyl alcohol at 25 is 59.2 the vapour pressure of a solution of volatile solute urea in ethyl alcohol is 51.3. What is the molality of solution?

We can use the concept of relative lowering of vapour pressure, according to which the relative lowering of vapour pressure is equal to the mole fraction of the solute. One can easily find the relative lowering in the vapour pressure, and thus, one can also calculate the mole fraction of urea in the solution. Also, on subtracting the mole fraction of urea from 1, one can get the mole fraction of ethyl alcohol. This can be easily related to th emolality of solution by converting the mole fraction into the amount of solute and solvent.