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A. Calculate the vapor pressure of a solution composed of 320 grams of acetone (C3H6O) and 205 grams of isopropanol (C3H7OH) at 39.5°C. The vapor pressures of acetone and isopropanol are 0.526 atm and torr, respectively.

B. Calculate the vapor pressure of a solution made up of 67 grams of galactose (C6H12O6) added to 800 mL of water at 100°C. The vapor pressure of water at 100°C is 101,325 Pa.

C. Calculate the vapor pressure of a solution composed of 952 grams of magnesium chloride added to 380 mL of water at 10°C. The vapor pressure of water is 9.2 mm Hg at this temperature.

Freezing Point Depression

D. What mass of sucrose (C12H22O11) must be dissolved in 150.0 g of ethanol to give a solution with a freezing point of 118.3°C? The Kf for ethanol is -1.99°C · kg / mol and the freezing point of ethanol is 114.6°C.

E. Calculate the boiling point and freezing point of 210. grams of substance Z after adding 21.3 grams of calcium nitrate. The boiling point of substance Z is 119°C and freezing point is -8°C. The Kb of substance Z is 2.38 C · kg / mol and the Kf is -1.13 C · kg / mol. Assume that there is no ion pairing in calcium nitrate.

F. 531 kilograms of substance S was dissolved in 1007 kilograms of formic acid. The new freezing point after adding substance S was -12.0°C. Calculate the molar mass of substance S. The freezing point depression constant Kf for formic acid is 2.77°C · kg / mol and the normal freezing point is 8°C. Substance S does not dissociate in formic acid.

G. What mass of fructose (C6H12O6) must be dissolved in 373 g of cyclohexane to give a solution with a freezing point of 0°C? The Kf for cyclohexane is 20.2°C · kg / mol and the normal freezing point of cyclohexane is 6.55°C.

Boiling Point Elevation

H. 7.00 grams of substance X was dissolved in 12.5 grams of benzene. The new boiling point after adding substance X was 85.1 °C. Calculate the molar mass of substance X. The boiling point elevation constant Kb for benzene is 2.65°C · kg / mol and the normal boiling point for benzene is 80.1 °C. Substance X does not dissociate in benzene.

I. 13.5 grams of substance Y was dissolved in 425 grams of acetic acid. The new boiling point after adding substance X was 121°C. Calculate the molar mass of substance X. The boiling point elevation constant Kb for acetic is 3.07°C · kg / mol and the normal boiling point is 118°C. Substance Y does not dissociate in acetic acid.

J. What mass of potassium phosphate must be dissolved in 862 g of chloroform to give a solution with a boiling point of 80.0°C? The Kb for chloroform is 3.88°C · kg / mol and the normal boiling point of 61.2°C. Assume there is no ion pairing in potassium phosphate.

Osmotic Pressure

K. Calculate the osmotic pressure at 25 degrees C of a .62 M barium fluoride solution in water. Assume that van ‘t Hoff factors are expected values. Would the calculated value be lower or higher than the actual value? Explain.

L. 1.51 L of an unknown solution was measured to cause 8.3 atm of osmotic pressure at 10 degrees C. Calculate the mols of the unknown solute. Assume that van ‘t Hoff factor = 1.

M. 0.143 M of an aluminum chloride solution was observed to exhibit 11.2 atm of osmotic pressure at 25 degrees C. Calculate the observed van’t Hoff factor for aluminum chloride.

Henry’s Law

N. The solubility of substance K in water is 5.11 x 10-7 mol/L at 25.0°C. Calculate the Henry’s law constant for substance K when the partial pressure of K above water is equal to 1.20 atm at 25.0°C. Use this information to calculate the solubility of K in water when partial pressure is equal to 1.97 at 25.0°C.

O. The solubility constant of substance T was determined to be 6.41 mol/L · atm at 25.0°C. Calculate the concentration of substance T dissolved in water if the partial pressure of substance T above water is 2.03 atm at 25.0°C.

P. 3.96 mol/L of substance D was dissolved in benzene. If the Henry’s law constant for substance D, kD = 12.6 mol/L · atm at 10.0°C, than calculate the partial pressure of substance D above benzene at 10.0°C.

Answers

A. 285 torr or .375 atm

B. 754 mm Hg or 100, 514 Pa

C. 3.80 mm Hg

D. 95.38 g

E. 123°C, -10.1°C

F. 73.0 g/mol

G. 21.8g

H. 297g/mol

I. 32.5 g/mol

J. 221g

K. 45 atm
The calculated value will be higher than the actual value because ion pairing will cause the van ‘t Hoff factor to be less than the expected value.

L. 0.0443 mol

M. 3.20

N. 4.26 x 10-7 mol/L · atm, 8.39 x 10-7 mol/L

O. 13.0 M

P. 0.314 atm

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