Part 1: At 55.0 C, what is the vapor pressure of a solution prepared by dissolvi

Question

Part 1:

At 55.0 C, what is the vapor pressure of a solution prepared by dissolving 78.4 g of LiF in 259 g of water? The vapor pressure of water at 55.0 C is 118 mmHg. Assume complete dissociation of the solute. Express your answer to three significant figures and include the appropriate units.

Part 2:

The solvent for an organic reaction is prepared by mixing 50.0 mL of acetone (C3H6O) with 50.0 mL of 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? Compound Vapor pressure (mmHg) Density (g/mL) acetone 230.0 0.791 ethyl acetate 95.38 0.900 Express your answer to three significant figures and include the appropriate units.

Explanation / Answer

P0 - P/P0 = n1/n1+n2
118 - P/118 = (78.4/26)/((78.4/26)+(259/18))
p = 97.556 mmHg

mass of acetone = 50 * 0.791 = 39.55 g
mass of ethyl acetate = 0.9*50 = 45 g
Ptot * V tot = (n1 + n2) * R * T
Ptot * (50+50)/1000 = ((39.55/58)+(45/88))*0.0821 * 298
Ptot = 291.94 mm Hg = 292 mm Hg

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