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Glycerin, , is a nonvolatile liquid. What is the vapor pressure of a solution made by adding glycerin to at

Sagot :

Complete question is;

Glycerin, C3H8O3, is a nonvolatile liquid. What is the vapor pressure of a solution made by adding 164 g glycerin to 338 mL H2O ​at 39.8°C?

The vapor pressure of pure water at 39.8°C is 54.74 torr and its density is 0.0992 g/cm³

Answer:

28 torr

Explanation:

Let's first find the number of moles of water in 338 mL.

Molar mass of water = 18 g/mole

Formula for number of moles = mass/molar mass.

Mass = density × volume = 0.0992 × 338 = 33.5296 g

Thus;

Number of moles = 33.5296/18 = 1.863 moles.

Let's use the same procedure to find the Number of moles of glycerine.

Molar mass of glycerine from online values = 92.1 g/mol

Thus;

n_glycerine = (mass)/92.1

We have mass and density as 164 g and 0.0992 g/cm³ respectively.

n_glycerine = 164/92.1

n_glycerine = 1.78

Total moles of solution = 1.863 + 1.78 = 3.643 moles

We are told that The vapor pressure of pure water at 39.8°C is 54.74 torr

Thus, since water dominates, then vapour pressure of solution = (1.863/3.643) × 54.74 ≈ 28 torr