Q: Which equation correctly expresses Raoult's Law for the vapor pressure of a solvent above a solution?

$P_{solvent} = X_{solvent} \times P^o_{solvent}$

Q: A physician dissolves 21.5 mg of a protein in water to make 1.50 mL of solution at 5.0°C. The osmotic pressure is measured to be 3.61 torr. What is the molar mass of the protein? ($R = 0.0821\ \mathrm{L\cdot atm/K\cdot mol}$, $T = 278.15\ \mathrm{K}$)

$6.89 \times 10^4\ \mathrm{g/mol}$

Question 1

Which of the following statements best explains why a salt solution conducts electricity while a sugar solution does not?

Accepted Answer

Salt dissociates into ions in water, while sugar does not produce ions.

Question 2

Which of the following is a strong electrolyte when dissolved in water?

Accepted Answer

NaCl

Question 3

A solution is prepared by dissolving 2.00 moles of Ca(NO3)2 in enough water to make 1.00 L of solution. What is the concentration of nitrate ions, [NO3-], in the solution?

Accepted Answer

$[NO_3^-] = 6.00\ \mathrm{M}$

Question 4

Which process is always exothermic during solution formation?

Accepted Answer

Mixing of solute and solvent particles

Question 5

Given the following enthalpy changes for a solution process: $\Delta H_{solute} = +10\ \mathrm{kJ}$, $\Delta H_{solvent} = +5\ \mathrm{kJ}$, $\Delta H_{mix} = -20\ \mathrm{kJ}$, what is the overall enthalpy change ($\Delta H_{soln}$)?

Accepted Answer

$\Delta H_{soln} = -5\ \mathrm{kJ}$

Question 6

Which of the following best describes a supersaturated solution?

Accepted Answer

It contains more solute than the equilibrium concentration and is unstable.

Question 7

According to Henry's Law, what happens to the solubility of a gas in a liquid if the partial pressure of the gas above the liquid is doubled?

Accepted Answer

The solubility is doubled.

Question 8

A 0.5 L bottle of cola is sealed at 25°C with a CO2 pressure of 4 atm. Given $k_H = 3.3 	imes 10^{-2}\ \mathrm{mol/L\cdot atm}$ and the molar mass of CO2 is 44.01 g/mol, what mass of CO2 is dissolved in the cola?

Accepted Answer

$2\ \mathrm{g}$

Question 9

Which of the following concentration units is defined as moles of solute per kilogram of solvent?

Accepted Answer

Molality

Question 10

A solution is made by dissolving 142 g of isopropyl alcohol ($C_3H_7OH$) and 58.0 g of water. What is the mole fraction of isopropyl alcohol?

Accepted Answer

$0.423$

Question 11

Which of the following statements about colligative properties is correct?

Accepted Answer

They depend only on the number of solute particles.

Question 12

Calculate the freezing point of a solution containing 685 g of ethylene glycol ($C_2H_6O_2$) in 2075 g of water. ($K_f$ for water = $1.86\ ^\circ\mathrm{C}/m$; molar mass of $C_2H_6O_2 = 62.07\ \mathrm{g/mol}$)

Accepted Answer

$-9.89\ ^\circ\mathrm{C}$

Question 13

Which solution will have the highest boiling point?

Accepted Answer

0.50 M MgCl$_2$

Question 14

What is the van't Hoff factor ($i$) for Na$_2$SO$_4$ in water, assuming complete dissociation?

Accepted Answer

$i = 3$

Question 15

Which equation correctly expresses Raoult's Law for the vapor pressure of a solvent above a solution?

Accepted Answer

$P_{solvent} = X_{solvent} 	imes P^o_{solvent}$

Question 16

A solution is prepared by dissolving 10.0 mL of glycerol ($C_3H_8O_3$) in 500. mL of water at 50°C. The vapor pressure of pure water at this temperature is 92.5 torr. What is the vapor pressure lowering ($\Delta P$) caused by the glycerol?

Accepted Answer

$0.461$ torr

Question 17

Which of the following best describes osmosis?

Accepted Answer

The flow of solvent from low to high solute concentration through a semipermeable membrane.

Question 18

A physician dissolves 21.5 mg of a protein in water to make 1.50 mL of solution at 5.0°C. The osmotic pressure is measured to be 3.61 torr. What is the molar mass of the protein? ($R = 0.0821\ \mathrm{L\cdot atm/K\cdot mol}$, $T = 278.15\ \mathrm{K}$)

Accepted Answer

$6.89 	imes 10^4\ \mathrm{g/mol}$

Question 19

Which of the following is an example of the Tyndall effect?

Accepted Answer

A beam of sunlight is visible as it passes through fog.

Solutions and Their Properties: Electrolytes, Solubility, and Colligative Effects

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