Answer: The vapor pressure of the solution is 186.4 torr
Explanation:
As the relative lowering of vapor pressure is directly proportional to the amount of dissolved solute.
The formula for relative lowering of vapor pressure will be,
where,
= relative lowering in vapor pressure
i = Van'T Hoff factor = 1 (for non electrolytes)
= mole fraction of solute =
Given : 21.5 g of lactose is present in 200.0 g of water.
moles of solute (lactose) =
moles of solvent (water) =
Total moles = moles of solute (lactose) + moles of solvent (water) = 0.0628+ 11.1 = 11.1628
= mole fraction of solute =
Thus the vapor pressure of the solution is 186.4 torr