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Chem 116 - General Chemistry II

Colligative Properties

Colligative Properties - Freezing Point I

The aqueous solution with the lowest freezing point is:
A. 0.1 m FeCl2
B. 0.2 m HCl
C. 0.2 m CH3OH (methanol)
D. 0.2 m HF
E. pure water

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Colligative Properties - Freezing Point II

The freezing point of a solution made by dissolving 0.084 mol NaNO3 (assume complete dissociation) in 350. g of water is expected to be _________.
KF(H2O)=1.86 °C-kg/mol

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Colligative Properties - FP with van't Hoff factor

A solution made by dissolving 23.5 g MgSO4 in 250. g of water has a freezing point of -2.51˚C. Based upon this data, the van’t Hoff factor (i) for MgSO4 is:_____
KF(H2O)=1.86 °C-kg/mol

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Colligative Properties - Osmotic Pressure

An aqueous solution made by dissolving 0.0840 g of an unknown nonelectrolyte in enough water to prepare 500.0 mL of solution exhibits an osmotic pressure of 5.22 mm Hg at 23.5˚C. The molar mass of the unknown nonelectrolyte is:_____

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Colligative Properties - Vapor Pressure I

What is the mole fraction of candle wax in a solution made by dissolving 10.0 g of solid candle wax (C22H46) in 40.0 g of the liquid solvent carbon tetrachloride (CCl4)?

At 20.°C, what is the vapor pressure of the solution specified in the preceding question? Candle wax is a nonvolatile, non-electrolyte. The vapor pressure of pure liquid CCl4 is 155 torr at 20.°C.

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Colligative Properties - Vapor Pressure II

A solution of liquid heptane (P˚=36.0 torr at 20˚C ) and liquid pentane (P˚=422 torr at 20˚C) has a heptane mole fraction of 0.80. The vapor pressure of this solution is ____ and the mole fraction of heptane in the vapor is expected to be ________.

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Freezing Point Depression

What is the freezing point of a 0.35 m AlCl3 solution?
(Kf = 1.86 kg ˚C/mol)

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Boiling Point of NaCl Solution

How many grams of NaCl is required to dissolve in 50.0 grams of water to raise the boiling point of the solution to 102.60˚C?

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Henry's Law

The Henry's Law Constant of methyl bromide, a gas used as a soil fumigating agent, is k = 0.159 mol L-1 atm-1 at 25 C. What is the solubility (in mol/L) of methyl bromide in water at 25 C and a partial pressure of 125 mm Hg?

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Henry's Law

The solubility of carbon dioxide in water is 2.4 X 10-2 M at 25C and 0.750 atm pressure. What is the value of Henry's Law Constant for carbon dioxide in mol L-1 atm-1?

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Henry's Law

What is the value of Henry's Law constant if 27 g of gaseous acetylene (C2H2, 26.04 g/mol) is dissolved in 0.50 L of liquid acetone at a pressure of 2.0 atm?

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Vapor Pressure

What is the vapor pressure (in mm Hg) of a solution prepared by dissolving 5.00 g of benzoic acid (C7H6O2, 122.13 g/mol) in 100.0 g of ethyl alcohol (C2H6O, 46.08 g/mol) at 35C? The vapor pressure of pure ethyl alcohol at 35C is 100.5 mm Hg.

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Vapor Pressure

What mass of sucrose (342.3 g/mol) must be added to 320. g of water to lower the vapor pressure by 1.5 mm Hg at 25C? The vapor pressure of water at 25C is 23.8 mm Hg.

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Miscible Liquids

Consider a liquid solution containing 25.0 g of water (18.02 g/mol) dissolved in 100.0 g of ethanol (C2H5OH, 46.08 g/mol) at 25 C. The vapor pressure of pure water is 23.8 mm Hg and that of pure ethyl alcohol is 61.2 mm Hg at 25C.

A. Which liquid component is more volitile, ethanol or water?

B. What is the mole fraction of ethyl alcohol in the liquid phase?

C. What is the vapor pressure of ethyl alcohol and the vapor pressure of water above the solution? What is the total pressure of the solution?

D. What is the mole fraction of ethyl alcohol in the gas phase?.

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Boiling Point

Determine the boiling point of the following solution:

Kb(water) = 0.52 C kg/mol

Assume 100 % dissociation of Sr(ClO3)2 in solution.

A. 0.90 m sugar

B. 0.90 m Sr(ClO3)2

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Equilibrium Using ICE Tables

Consider the theoretical equilibrium shown below. Given that the equilibrium concentration of B is 2.20 M, determine the numerical value of Kc.

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Determining Molar Mass

What is the molar mass of sucrose (table sugar) if a solution prepared by dissolving 0.822 g of sucrose in 300.0 mL of solution has an osmotic pressure of 149 mm Hg at 298 K?

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Osmotic Pressure

What osmotic pressure (in atm) would you expect for the following solution? Assume complete dissociation.

5.00 g of NaCl (58.44 g/mol) in 350.0 mL of water at 50 C.

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