Answer
24.1 torr
Work Step by Step
The vapor pressure of a solution is calculated with Raoult's law
Psolution = Xsolvent * Psolvent
where Xsolvent represents the mole fraction of the solvent and Psolvent is the vapor pressure of water in torr.
To calculate the mole fraction of the solvent calculate the amount of moles of solute (C3H8O3 = 34.0g * (1 mole / 92.09382g) = 0.369189 mol.
We're also going to need to convert H2O to moles to perform this calculation.
515.0g * (1 mole / 18.015g) = 28.58684 mol.
(28.58684mol / 28.58684 - 0.369189) = 1.01308 * 23.76 torr = 24.1 torr
