Multiple Choice
A solution is prepared by dissolving 40.0 g of sucrose, C12H22O11, in 250. g of water at 25°C. What is the vapor pressure of the solution if the vapor pressure of pure water at 25°C is 23.76 mm Hg?
14. Solutions
Vapor Pressure Lowering (Raoult's Law)
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The colligative molality of seawater is approximately 1.10 m. Calculate the vapor pressure of seawater at 20 °C. The vapor pressure of pure water at 20 °C is 17.54 Torr. What is the vapor pressure of seawater?
A
18.00 Torr
B
17.00 Torr
C
15.50 Torr
D
16.35 Torr
Verified step by step guidance1
Identify the colligative property involved: In this case, we are dealing with vapor pressure lowering, which is a colligative property.
Use Raoult's Law to determine the vapor pressure of the solution. Raoult's Law states that the vapor pressure of a solution (P_solution) is equal to the mole fraction of the solvent (X_solvent) times the vapor pressure of the pure solvent (P_pure). The formula is: .
Calculate the mole fraction of the solvent. The mole fraction of the solvent can be found using the formula: , where is the molality and is the van't Hoff factor. For seawater, assume due to the dissociation of salts.
Substitute the given values into the mole fraction formula: .
Calculate the vapor pressure of the seawater using the mole fraction and Raoult's Law: .
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