1. A 0.14-g sample of a purified protein is dissolved in water to give 2.0 mL of

Question

1. A 0.14-g sample of a purified protein is dissolved in water to give 2.0 mL of solution. The osmotic pressure is found to be 17.2 torr at 25°C. Calculate the protein's molar mass. Molar mass = __________ g/mol 2. An aqueous solution of 13.1 g of catalase, an enzyme found in the liver, has a volume of 1.00 L at 27oC. The solution’s osmotic pressure at 27oC is found to be 0.976 torr. Calculate the molar mass of catalase. Molar mass = __________ g/mol 3.A solution contains 4.05 g of a nonvolatile pure hydrocarbon in 95 g acetone. The boiling points of pure acetone and the solution are 55.95oC and 56.50oC, respectively. The molal boiling point constant of acetone is 1.71oC kg/mol. What is the molar mass of the hydrocarbon? Molar mass = ________ g/mol 4. What mass of glycerin, a nonelectrolyte, must be dissolved in 200.0 g water to give a solution with a freezing point of –4.10°C? Mass = ______ g

Explanation / Answer

1)

P = 17.2 / 760 = 0.0226 atm

T = 25 + 273 = 298 K

P = M R T

0.0226 = M x 0.0821 x 298

M = 9.25 x 10^-4 molar

(0.14 / molar mass ) x 1000 / 2 = 9.25 x 10^-4

molar mass = 75673 g/mol

2)

osmotic pressure = mass x R T / molar mass x volume

0.976 /760 = 13.1 x 0.0821 x 298 / molar mass x 1

molar mass = 249571 g/mol

3)

delta T = 55.95oC - 56.50oC = 0.55

delta T   = kb x mass x 1000 / molar mass of solute x mass of sovlent

0.55 = 1.71 x 4.05 x 1000 / molar mass x 95

molar mass = 132.5 g/mol

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