the vapor pressure of pure water at 25C is 23.8 torr. determine the vapor pressure (torr) of water at 25 C above a solution prepared by dissolving 35g of urea (a nonvolatile, non-electrolyte, MW = 60.0G/MOL) IN 76G of water.
answer:21
i just want to know the steps bc im confused... help?
Step 1. Determine mole fraction water.
a. moles urea = grams/molar mass = 35/60 = 0.583
b. moles H2O = 76/18 = 4.222
c. total moles = 4.805
d. XH2O = 4.222/4.805 = ??
Step 2.
Psoln = Xsolvent*Posolvent
where Po = normal vapor pressure of the solvent.
To determine the vapor pressure of water above a solution, you can use Raoult's Law, which states that the vapor pressure of a component in a solution is equal to the vapor pressure of the pure component multiplied by its mole fraction.
Mole fraction (also known as mole fraction concentration) is the ratio of the number of moles of a component to the total moles in the solution.
To solve this problem, follow these steps:
Step 1: Calculate the number of moles of urea (nonvolatile solute) in the solution:
First, find the moles of urea:
moles of urea = mass of urea / molar mass
moles of urea = 35 g / 60.0 g/mol
moles of urea = 0.583 mol
Step 2: Calculate the number of moles of water (solvent) in the solution:
First, find the moles of water:
moles of water = mass of water / molar mass
moles of water = 76 g / 18.0 g/mol
moles of water = 4.222 mol
Step 3: Calculate the total moles in the solution:
total moles = moles of urea + moles of water
total moles = 0.583 mol + 4.222 mol
total moles = 4.805 mol
Step 4: Calculate the mole fraction of water:
mole fraction of water = moles of water / total moles
mole fraction of water = 4.222 mol / 4.805 mol
mole fraction of water = 0.879
Step 5: Use Raoult's Law to calculate the vapor pressure:
vapor pressure of water in the solution = vapor pressure of pure water * mole fraction of water
vapor pressure of water in the solution = 23.8 torr * 0.879
vapor pressure of water in the solution = 20.893 torr
Therefore, the vapor pressure of water above the solution is approximately 21 torr.