Chemistry of Solutions - Vapor Pressure of Pure Benzene - Science Assignment Help

Assignment Task:

Task:

Please enter your final answer in the appropriate box or circle only one right answer. Multiple choices are 1 point each.
1. ( 5 points )
At a given temperature, you have a mixture of
benzene (vapor pressure of pure benzene = 745.0 torr)
and toluene (vapor pressure of pure toluene = 290.0 torr).
The mole fraction of benzene in the vapor above the solution is 0.5432.
Assuming ideal behavior, calculate the mole fraction of toluene in the solution.

Use the following to answer questions 2 a-d :
Consider the following equilibrium: 2H2(g) + X2(g) 2H2X(g) + energy

2a. Addition of X2 to a system described by the above equilibrium
a) will cause [H2] to decrease
b) will cause [X2] to decrease
c) will cause [H2X] to decrease
d) will have no effect
e) cannot possibly be carried out

2b. Addition of argon to the above equilibrium
a) will cause [H2] to decrease
b) will cause [X2] to increase
c) will cause [H2X] to increase
d) will have no effect
e) cannot possibly be carried out

2c. Increasing the pressure by decreasing the volume will cause
a) the reaction to occur to produce H2X
b) the reaction to occur to produce H2 and X2
c) the reaction to occur to produce H2 but no more X2
d) no reaction to occur
e) X2 to dissociate

2d. Increasing the temperature will cause
a) the reaction to occur to produce H2X
b) the reaction to occur to produce H2 and X2
c) the reaction to occur to produce H2 but no more X2
d) no reaction to occur
e) an explosion

A 0.1000 gram sample of a compound is dissolved in enough water to form 25.00 mL of solution. This solution has an osmotic pressure of 294.8 torr at 25.00°C. If it is assumed that each molecule of the solute dissociates into two particles (in this solvent), what is the molar mass of this solute?

4a. Consider pure water separated from an aqueous sugar solution by a semipermeable membrane, which allows water to pass freely but not sugar. After some time has passed, the concentration of sugar solution:
a) will have increased
b) will have decreased
c) will not have changed
d) might have increased or decreased depending on other factors
e) will be the same on both sides of the membrane

4b. The observed van't Hoff factor for an electrolyte is less than the expected factor because of __________.
a) electrolytic repulsion
b) complete dissociation
c) coagulation
d) ion pairing
e) gelation

4c. A solute added to a solvent raises the boiling point of the solution because:
a) The temperature to cause boiling must be great enough to boil not only the solvent but also the solute.
b) The solute particles raise the solvent's vapor pressure, thus requiring a higher temperature to cause boiling.
c) The solute particles lower the solvent's vapor pressure, thus requiring a higher temperature to cause boiling.
d) The solute increases the volume of the solution, and an increase in volume requires an increase in the temperature to reach the boiling point (derived from PV = nRT).
e) Two of the above are correct.

4d. A solution of two liquids, A and B, shows negative deviation from Raoult's law. This means that:
a) The molecules of A interact strongly with other A-type molecules.
b) The two liquids have a positive heat of solution.
c) Molecules of A interact weakly, if at all, with B molecules.
d) Molecules of A interact more strongly with B than A with A, or B with B.
e) The molecules of A hinder the strong interaction between B molecules.

4e. Which of the following concentration measures will change in value as the temperature of a solution changes?
a) mass percent
b) mole fraction
c) molality
d) molarity
e) all of these

4f. In a 0.1 molar solution of NaCl in water, which one of the following will be closest to 0.1?
a) The mole fraction of NaCl.
b) The mass fraction of NaCl.
c) The mass percent of NaCl.
d) The molality of NaCl.
e) All of these are about 0.1.

5. What partial pressure of N2 gas is required ( 5 points )
in order for 0.001567 g of the gas to dissolve in 22.47 mL of pure water?
The Henry's law constant for nitrogen gas is 6.100 × 10–4 M atm–1

6. Thyroxine, an important hormone that controls the rate of metabolism in the body, ( 5 points )can be isolated from the thyroid gland.
If 0.4550 g of thyroxine is dissolved in 10.0000 g of benzene, the freezing point of the solution could be measured as 5.141°C. Pure benzene freezes at 5.444°C and has a value for the molal freezing point depression constant of Kf of 5.12°C/m.
What is the approximate molar mass of thyroxine?

7. ( 5 points )
A mixture of 8.565 moles of A, 4.879 moles of B, and 9.012 moles of C is placed in a 1.00 L container at a certain temperature. At equilibrium, the number of moles of B is 5.987. Calculate the equilibrium constant for the reaction:

A (g) + 2 B (g) ? 3 C (g)

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