Chapter 13 Homework Flashcards Preview

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Flashcards in Chapter 13 Homework Deck (19)
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1
Q

A solution is formed from 1.56 g of an unknown hydrocarbon dissolved in 75.0 g of ethanol. The normal boiling point of ethanol is 78.26°C. With the dissolved hydrocarbon, the solution boils at 78.39°C. What is the molecular weight of the compound?

For ethanol, Kb = 1.22 K kg / mol

A

194 g / mol

2
Q

Look at the two graphs that show the deviations in Raoult’s law.

Which of the following correctly correlates the colored plots with their correct solution type?

A

black: an endothermic solution event
green: an ideal (nonvolatile solute) solution
red: an exothermic solution event

3
Q

What is the minimum molarity required for sap to rise to the top of a 100.0 m sequoia tree at 25.0°C? Assume that the rising of the sap is due entirely to osmosis, and that the density of the sap is 1.00 g/cm3. The acceleration due to gravity is 9.8 m/s2, the ideal gas constant is 0.0821 L•atm/(mol•K), 1 atm = 1.01 × 105 Pa, and 1 Pa = 1 kg/(m•s2 ).

A

0.40 M

4
Q

A gaseous solution is made up of 0.289 moles of nitrogen gas and 0.433 moles of oxygen gas. What are the mole fractions of nitrogen and oxygen, respectively?

A

0.400 and 0.600

5
Q

In the context of a liquid-vapor system, what is a dynamic equilibrium?

A

a condition in which a forward process and its reverse process occur at equal rates so that there is no net change in the amount of either liquid or vapor.

6
Q

A solution is made by dissolving 50.0 g of glucose (C6H12O6, molar mass = 180.1 g / mol) in 294 g of water. What is the molality of this solution?

A

0.944 m

7
Q

Which of the following statements about solutions is not a correct definition for the term named in that statement?

A

Hydration is the solvation of a solvent by water.

8
Q

Suppose that you have a 1.23 M solution whose solute has a molar mass of 289.7 g / mol. What is the mass of solute in one liter of the solution?

A

356 g

9
Q

Consider the form of Henry’s Law.

Pgas = kHXgas

The value of the Henry’s Law constant is found to be temperature-dependent and generally increases with increasing temperature. This indicates that

A

gases become less soluble with increasing temperature

10
Q

Consider water in equilibrium with air. What is the concentration of nitrogen in the water at 25°C if the Henry’s Law constant for nitrogen is 6.48 × 10−4 mol / (L • atm) and if the partial pressure of nitrogen in air is 0.786 atm?

A

5.09 × 10^−4 M

11
Q

Suppose you have a flask with some water in it. You add some dichloromethane, CH2Cl2, which separates and forms a second layer below the water. Which statement about this event is not correct?

A

The mass of dichloromethane that you added is greater than the mass of the water originally present..

12
Q

Which of the following statements about solutions is not correct?

A

High solubility in water implies relatively weak bonding between particles.

13
Q

Suppose you add 3.85 g of naphthalene, C10H8, to 59.2 g of benzene, C6H6. The molar masses of naphthalene and benzene are 128.17 g / mol and 78.0 g / mol respectively. What are the mole fractions of naphthalene and benzene, respectively, in this solution?

A

0.0380; 0.962

14
Q

Three vapor pressure curves are plotted against temperature. One for pure water, one for a solvent dissolved in water with molality X, and one of the same solvent dissolved in water to a molality of 2X. Which curve represents the vapor pressure curve for the 2X solution?

A

D

15
Q

Suppose that you have oxygen in solution (of water) at 25°C. If the Henry’s law constant = 4.3 × 10^3 atm and the partial pressure of oxygen is 0.22 atm, what is the mole fraction of oxygen in the solution?

A

5.11 × 10^−5

16
Q

Which of these colligative properties is the most sensitive for determining molecular weight?

A

Osmosis

17
Q

A certain type of sugar dissolves in water, but the solution created does not conduct electricity. Therefore, the sugar does not form ions when dissolved in solution. When 10.0 g of this sugar are dissolved in 25.0 g of water, the freezing point of the solution is −5.0°C. If the freezing point depression constant for water (Kf) is 1.86°C/m, what is the molar mass of the sugar?

A

150 g/mol

18
Q

Suppose 0.10 moles of CaCl2 are dissolved in 1.0 kg of water. In aqueous solution, CaCl2 completely ionizes. Which of the following is the correct molality for Ca2+ and Cl −?

A

The molality of Ca2+ is 0.10 and the molality of Cl − is 0.20.

19
Q

What is the boiling point of a solution that contains 5.0 g of NaCl dissolved in 25 g of water (Kb for water is 0.51)?

A

103.5°C

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