Question

Calculate the vapor pressure of a solution prepared by dissolving 0.500 mol of a non-volatile solute in 275 g of hexane (C6H14, MM = 86.18 g/mol) at 49.6°C. P°(hexane) = 400.0 torr at 49.6°C.

Answer 1

Answer:

The vapor pressure = 345.8 torr

Explanation:

Step 1: Data given

Number of molesof a non-volatile solute = 0.500 moles

mass of hexane = 275 grams

Molar mass of hexane = 86.18 g/mol

Temperature =49.6 °C

P°(hexane) = 400.0 torr at 49.6°C.

Step 2: Calculate moles solvent

moles of solvent = 275 grams / 86.18 g/mol = 3.19 mol

Mol fraction of the solvent = 3.19 moles / (0.500 + 3.19) = 0.8645

Step 3: Calculate the vapor pressure

P = P° * Xsolvent

⇒ with Xsolvent = mol fraction of the solvent =  0.8645

 ⇒ with P° hexane =400.0 torr

P =  400.0 * 0.8645 = 345.8 torr

The vapor pressure = 345.8 torr