Question

The vapor pressure of chloroform is 173.11 mm Hg at 25 °C. A nonvolatile, nonelectrolyte that dissolves in chloroform is aspirin. Calculate the vapor pressure of the solution at 25 °C when 9.322 grams of aspirin, C9H8O4 (180.1 g/mol), are dissolved in 263.4 grams of chloroform. chloroform = CHCl3 = 119.40 g/mol. VP(solution) = mm Hg

Answer 1

Answer:

VP (solution) = 171.56 mmHg

Explanation:

Vapor pressure of pure solvent(P°) - Vapor pressure of solution (P') = P° . Xm

Let's replace the data:

173.11 mmHg - P' = 173.11 mmHg . Xm

Let's determine the Xm (mole fraction for solute)

Mole fraction for solute = Moles of solute / Total moles

Total moles = Moles of solute + moles of solvent.

Let's determine the moles

Moles of solvent → 623.4 g / 119.4 g/mol = 5.22 moles

Moles of solute → 9.322 g / 180.1 g/mol = 0.052 moles

Total moles = 0.052 + 5.22 = 5.272 moles

Xm = 0.052 moles / 5.272 moles = 0.009 → 9/1000

173.11 mmHg - P' = 173.11 mmHg . 9/1000

P' = - (173.11 mmHg . 9/1000 - 173.11 mmHg)

P' = 171.56 mmHg

Answer 2

Answer:

The vapor pressure of the solution is 169.25 mm Hg

Explanation:

Step 1: Data given

Vapor pressure of pure chloroform at 25 °C = 173.11 mm Hg

Mass of aspirin = 9.322 grams

Molar mass of aspirin = 180.1 g/mol

Mass of chloroform = 263.4 grams

Molar mass chloroform = 119.40 g/mol

Step 2: Calculate moles of aspirin

Moles Aspirin = mass aspirin / molar mass aspirin

Moles aspirin = 9.322 grams / 180.1 g/mol

Moles aspirin = 0.05176 moles

Step 3: Calculate moles of chloroform

Moles chloroform = 263.4 grams / 119.40 g/mol

Moles chloroform = 2.206 moles

Step 4: Calculate mol fraction of chloroform

Mol fraction chloroform = moles chloroform / total moles

Mol fraction chloroform = 2.206 moles / (0.05176 + 2.206 )

Mol fraction chloroform = 0.9777

Mol fraction aspirin = 1 - 0.9777 = 0.0223

Step 5: Calculate the vapor pressure of the solution

Vapor pressure solution = Mol fraction chloroform * vapor pressure chloroform

Vapor pressure solution = 0.9777 * 173.11 mm Hg

Vapor pressure solution = 169.25 mm Hg

The vapor pressure of the solution is 169.25 mm Hg