Question

The solvent for an organic reaction is prepared by mixing 50.0 mL of acetone (C3H6O) with 49.0 mLof ethyl acetate (C4H8O2). This mixture is stored at 25.0 ∘C. The vapor pressure and the densities for the two pure components at 25.0 ∘C are given in the following table. What is the vapor pressure of the stored mixture? (Express your answer to three significant figures and include the appropriate units.)

Compound	Vapor pressure (mmHg)	Density (g/mL)
acetone	230.0	0.791
ethyl acetate	95.38	0.900

Answer 1

Density of Acetone = Mass of Acetone/Volume of acetone

Mass of Acetone = 0.791 gm/ml * 50 ml = 39.55 gms

Molar mass of Acetone(C3H6O) = 3 * 12 + 6 * 1 + 16 = 36 + 22 = 58 gm/mol

Density of Ethyl Acetate = Mass of Ethyl Acetate/Volume of Ethyl Acetate

Mass of Ethyl Acetate = 0.900 gm/ml * 49 ml = 44.1 gms

Molar mass of Ethyl Acetate = 4 * 12 + 8 * 1 + 2 * 16 = 88 gm/mol

Number of moles of acetone = 39.55/58 = 0.6818 moles

Number of moles of Ethyl Acetate = 44.1/88 = 0.5011 moles

Mole fraction of acetone = 0.6818/(0.6818+0.5011) = 0.5736

Mole fraction of Ethyl acetate = 1 - 0.5736 = 0.4236

Pressure of Solution = 0.4236 * 95.38 + 0.5736 * 230

=> 172.55 mm Hg