calculate the vapor pressure of a solution made by dissolving 61.7g (molar mass= 60.06g/mol) of Urea in 212ml of water at 35C. what is the vapor pressure lowering? the vapor pressure of water at 35c =31.82 mmHg
mols urea = grams/molar mass
mols H2O = grams/molar mass
Xurea = nurea/total mols from above.
XH2O = nH2O/total mols.
PH2O = Xurea*PoH2O
Lowering is
Plowering = XH2O*PoH2O
To calculate the vapor pressure of a solution and the vapor pressure lowering, you will need to use Raoult's law. Raoult's law states that the vapor pressure of a solvent above a solution is directly proportional to the mole fraction of the solvent in the solution.
Step 1: Calculate the mole fraction of the solvent (water).
To determine the mole fraction of the solvent, divide the moles of water by the total moles of solute and solvent.
Moles of water = (volume of water in liters) x (density of water) / (molar mass of water)
Given:
Volume of water = 212 ml = 0.212 L
Density of water = 1 g/mL (approximately)
Molar mass of water = 18.015 g/mol
Moles of water = (0.212 L) x (1 g/mL) / (18.015 g/mol)
Step 2: Calculate the moles of solute (Urea).
To determine the moles of solute, divide the mass of solute by the molar mass of Urea.
Moles of Urea = Mass of Urea / Molar mass of Urea
Given:
Mass of Urea = 61.7 g
Molar mass of Urea = 60.06 g/mol
Moles of Urea = 61.7 g / 60.06 g/mol
Step 3: Calculate the total moles of solute and solvent.
To determine the total moles of solute and solvent, add the moles of solute and moles of solvent.
Total moles = Moles of Urea + Moles of water
Step 4: Calculate the mole fraction of water.
To determine the mole fraction of water, divide the moles of water by the total moles.
Mole fraction of water = Moles of water / Total moles
Step 5: Calculate the vapor pressure of the solution.
To determine the vapor pressure of the solution, multiply the mole fraction of water by the vapor pressure of pure water.
Vapor pressure of the solution = Mole fraction of water x Vapor pressure of pure water
Step 6: Calculate the vapor pressure lowering.
To determine the vapor pressure lowering, subtract the vapor pressure of the solution from the vapor pressure of pure water.
Vapor pressure lowering = Vapor pressure of pure water - Vapor pressure of the solution
Using the given data:
Step 1: Moles of water = (0.212 L) x (1 g/mL) / (18.015 g/mol)
= 0.01175 mol
Step 2: Moles of Urea = 61.7 g / 60.06 g/mol
= 1.03 mol
Step 3: Total moles = Moles of Urea + Moles of water
= 1.03 mol + 0.01175 mol
= 1.04175 mol
Step 4: Mole fraction of water = Moles of water / Total moles
= 0.01175 mol / 1.04175 mol
≈ 0.0113
Step 5: Vapor pressure of the solution = Mole fraction of water x Vapor pressure of pure water
= 0.0113 x 31.82 mmHg
≈ 0.360 mmHg
Step 6: Vapor pressure lowering = Vapor pressure of pure water - Vapor pressure of the solution
= 31.82 mmHg - 0.360 mmHg
≈ 31.46 mmHg
Therefore, the vapor pressure lowering of the solution made by dissolving 61.7g of Urea in 212 ml of water at 35°C is approximately 31.46 mmHg.