The vapor pressure of pure water at 25 °C is 23.8 torr. Determine the vapor pressure (torr) of water
at 25 °C above a solution prepared by dissolving 35 g of urea (a nonvolatile, non-electrolyte, MW =
60.0 g/mol) in 75 g of water.
im not sure about the steps for problems like these...
moles urea = 35 g/molar mass urea.
moles H2O = 75 g/molar mass H2O.
total moles = moles urea + moles H2O.
mole fraction H2O = moles H2O/total moles
Psoln = XH2O*Ponormal
To determine the vapor pressure of water above a solution containing urea, you can use Raoult's law, which states that the vapor pressure of a component in a solution is directly proportional to its mole fraction in the solution.
Here are the steps to solve this problem:
Step 1: Calculate the number of moles of urea (C2H4O) and water (H2O) present in the solution.
Moles of urea:
Given mass of urea = 35 g
Molar mass of urea (MW) = 60.0 g/mol
Moles of urea = Mass of urea / Molar mass of urea
Moles of urea = 35 g / 60.0 g/mol
Moles of water:
Given mass of water = 75 g
Molar mass of water (MW) = 18.0 g/mol
Moles of water = Mass of water / Molar mass of water
Moles of water = 75 g / 18.0 g/mol
Step 2: Calculate the mole fraction of water in the solution.
Mole fraction of water (x_water) = Moles of water / Total moles
Total moles = Moles of urea + Moles of water
Step 3: Calculate the vapor pressure of water using Raoult's law.
Vapor pressure (P_water) = Mole fraction of water * Vapor pressure of pure water
Given vapor pressure of pure water at 25°C = 23.8 torr
Plug in the values calculated in steps 1 and 2 into Raoult's law equation:
P_water = x_water * 23.8 torr
Now you can calculate the vapor pressure of water above the solution by substituting the value of x_water into the equation.