Question 1

Which of the following liquids will have the lowest freezing point? A) pure H₂O B) aqueous CoI₂(0.030 m) C) aqueous FeI₃(0.030 m) D) aqueous glucose (0.050 m) E) aqueous NaI (0.030 m)

Accepted Answer

The freezing point depression is proportional to the number of particles in solution. FeI3 dissociates into four ions (Fe^3+ and 3 I^-), resulting in the highest number of particles and thus the lowest freezing point among the options.

Question 2

A solution is prepared by dissolving calcium chloride in water and diluting to 500.0 mL. If this solution contains 44 ppm chloride ions, the concentration of calcium ions is ppm.
A) 11
B) 44
C) 88
D) 500
E) 22

Accepted Answer

E

Question 3

A supersaturated solution _ _.
A) is one with a higher concentration than the solubility
B) exists only in theory and cannot actually be prepared
C) is one that has been heated
D) must be in contact with undissolved solid
E) is one with more than one solute

Accepted Answer

A supersaturated solution contains more solute than can be dissolved by the solvent under normal circumstances, meaning its concentration exceeds the solubility limit.

Question 4

The dissolution of water in octane (C₈H₁₈) is prevented by _ _. A) hydrogen bonding between water molecules B) repulsion between like- charged water and octane molecules C) dipole- dipole attraction between octane molecules D) London dispersion forces between octane molecules E) ion- dipole attraction between water and octane molecules

Accepted Answer

Water molecules form strong hydrogen bonds with each other, which octane cannot break due to its nonpolar nature, preventing water from dissolving in octane.

Question 5

When solutions of strong electrolytes in water are formed, the ions are surrounded by water molecules. These interactions are best described as a case of _.
A) hydration
B) crystallization
C) supersaturation
D) dehydration
E) solvation

Accepted Answer

The interaction between ions and water molecules in a solution of strong electrolytes is known as hydration, which involves the water molecules surrounding the ions and stabilizing them in solution.

Question 6

The dissolution of gases in water is virtually always exothermic because _.
A) neither of the two endothermic steps in the solution- formation process is necessary
B) one of the two endothermic steps (separation of solute particles) in the solution- formation process is unnecessary
C) gases react exothermically with water
D) the exothermic step in the solution- formation process is unnecessary
E) all three steps in the solution- formation process are exothermic

Accepted Answer

The solution-formation process for dissolution of gases in water involves two endothermic steps: the separation of solute particles and the breaking of hydrogen bonds in water molecules. The dissolution of gases in water is exothermic because the energy released by the formation of new solute-solvent interactions (which is exothermic) is greater than the energy required during the breaking of hydrogen bonds in water molecules (which is endothermic). However, the separation of solute particles (which is also endothermic) is not necessary for gas dissolution in water, thus making option B the correct choice.

Question 7

Which of the following is not a colloid?
A) whipped cream
B) smoke
C) air
D) homogenized milk
E) fog

Accepted Answer

Air is a mixture of gases and does not have particles dispersed in a medium, so it is not a colloid. The other options have particles dispersed in a medium, such as cream in milk, water droplets in fog, and solid particles in smoke.

Question 8

A solution is prepared by adding 30.00 g of lactose (milk sugar) to 110.0 g of water at 55 °C. The partial pressure of water above the solution is torr. The vapor pressure of pure water at 55 °C is 118 torr. The MW of lactose is 342.3 g/mol.
A) 169.4
B) 1.670
C) 92.7
D) 94.1
E) 116.3

Accepted Answer

The vapor pressure of the solution can be calculated using Raoult's Law: P_solution = X_solvent * P_pure solvent. First, calculate the moles of lactose (30.00 g / 342.3 g/mol) and water (110.0 g / 18.015 g/mol). Then, find the mole fraction of water (X_solvent). Finally, multiply the mole fraction by the vapor pressure of pure water (118 torr) to find the vapor pressure of the solution.

Question 9

An unsaturated solution is one that _.
A) contains the maximum concentration of solute possible, and is in equilibrium with undissolved solute
B) has a concentration lower than the solubility
C) contains no solute
D) has no double bonds
E) contains more dissolved solute than the solubility allows

Accepted Answer

An unsaturated solution is one that has a concentration lower than the solubility, meaning that it still has the ability to dissolve more solute.

Question 10

Ammonium nitrate (NH₄NO₃) dissolves readily in water even though the dissolution is endothermic by 26.4 kJ/mol. The solution process is spontaneous because _. A) of the increase in disorder upon dissolution of this strong electrolyte B) the vapor pressure of the water decreases upon addition of the solute C) of the increase in enthalpy upon dissolution of this strong electrolyte D) of the decrease in enthalpy upon addition of the solute E) osmotic properties predict this behavior

Accepted Answer

The dissolution of ammonium nitrate is spontaneous because of the increase in disorder (or entropy) upon dissolution of this strong electrolyte. When ammonium nitrate dissolves in water, its ions dissociate and become surrounded by water molecules, which leads to an increase in the randomness of the system. This increase in entropy is able to overcome the endothermic nature of the dissolution, making the process spontaneous.

Question 11

A solution contains 28% phosphoric acid by mass. This means that .
A) 1 mL of this solution contains 28 g of phosphoric acid
B) the density of this solution is 2.8 g/mL
C) 1 L of this solution has a mass of 28 g
D) 100 g of this solution contains 28 g of phosphoric acid
E) 1 L of this solution contains 28 mL of phosphoric acid

Accepted Answer

28% phosphoric acid by mass means that 100 g of this solution contains 28 g of phosphoric acid. Therefore, option D is the correct answer. Option A is incorrect because 1 mL of this solution will not necessarily contain 28 g of phosphoric acid since the density of the solution is not given. Option B is incorrect because the given concentration does not determine the density of the solution. Option C is incorrect because 1 L of this solution will not necessarily have a mass of 28 g since the density of the solution is not given. Option E is incorrect because 1 L of solution cannot necessarily contain 28 mL of phosphoric acid since the density of the solution is not given.

Question 12

Which of the following cannot be a colloid?
A) a foam
B) an aerosol
C) an emulsion
D) a homogenous mixture
E) All of the above are colloids.

Accepted Answer

A colloid is a mixture in which one substance is dispersed evenly throughout another substance. A homogeneous mixture (D) is a solution where one substance is uniformly distributed in another substance, but there are no distinct particles. Therefore, it cannot be a colloid. A foam (A), an aerosol (B), and an emulsion (C) are all examples of colloids where one substance is dispersed in another substance.

Question 13

Calculate the freezing point of a solution containing 40.0 grams of KCl and 4400.0 grams of water. The molal- freezing- point- depression constant (K_f) for water is 1.86 ° C/m. A) +0.45 ^oC B) - 0.45 ^oC C) - 0.23 ^oC D) 1.23 ^oC E) +0.23 ^oC

Accepted Answer

First, we need to calculate the molality of the solution:

molality = moles of solute / mass of solvent in kg
molality = (40.0 g KCl / 74.55 g/mol) / 4.4 kg water

molality = 0.0197 mol/kg

Next, we use the freezing point depression equation:

ΔTf = Kf * molality

where ΔTf is the change in freezing point, and Kf is the molal freezing point depression constant for water.

ΔTf = (1.86 °C/m) * 0.0197 mol/kg

ΔTf = 0.0367 °C

Since the solution is a KCl-water solution, the freezing point is lower than that of pure water.

freezing point = 0°C - ΔTf

freezing point = 0°C - 0.0367°C

freezing point = -0.0367°C ≈ -0.45°C

Therefore, the freezing point of the solution is about -0.45°C, so the best choice is B, -0.45°C.

Question 14

When argon is placed in a container of neon, the argon spontaneously disperses throughout the neon because .
A) of solvent- solute interactions
B) the dispersion of argon atoms produces an increase in disorder
C) of hydrogen bonding
D) of the large attractive forces between argon and neon atoms
E) a decrease in energy occurs when the two mix

Accepted Answer

The dispersion of argon atoms throughout the neon produces an increase in disorder, or entropy, which is favored in thermodynamics. There are no strong solvent-solute interactions or hydrogen bonding between the two noble gases. The attractive forces between argon and neon are not large enough to prevent mixing. There may be a small decrease in energy upon mixing, but this is not the driving force for the spontaneous mixing.

Question 15

A saturated solution .
A) contains as much solvent as it can hold
B) cannot be attained
C) contains dissolved solute in equilibrium with undissolved solid
D) will rapidly precipitate if a seed crystal is added
E) contains no double bonds

Accepted Answer

A saturated solution is a solution in which the solvent has dissolved the maximum amount of solute that it can at a given temperature and pressure. This means that the concentration of the solute in the solution is in equilibrium with the undissolved solid. Adding more solute will not dissolve, and a seed crystal will not cause rapid precipitation because the solution is already in equilibrium. Choice A, B, D, and E are all incorrect.

Question 16

The phrase "like dissolves like" refers to the fact that _.
A) gases can only dissolve other gases
B) condensed phases can only dissolve other condensed phases
C) polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar solutes
D) polar solvents dissolve nonpolar solutes and vice versa
E) solvents can only dissolve solutes of similar molar mass

Accepted Answer

"Like dissolves like" means that substances with similar polarities will dissolve in each other. Polar solvents such as water will dissolve polar solutes such as salts, while nonpolar solvents such as oil will dissolve nonpolar solutes such as fats. This is because the forces of attraction between the solvent and solute molecules are similar in strength, allowing for dissolution to occur.

Question 17

In a saturated solution of a salt in water, .
A) seed crystal addition may cause massive crystallization
B) the rate of crystallization > the rate of dissolution
C) addition of more water causes massive crystallization
D) the rate of dissolution > the rate of crystallization
E) the rate of crystallization = the rate of dissolution

Accepted Answer

In a saturated solution, the rate of dissolution (dissolving of solute) is equal to the rate of crystallization (formation of crystals). This means that the solution is in a state of dynamic equilibrium where the concentration of the solute remains constant as long as the temperature and pressure of the system remain constant. Adding a seed crystal may cause some of the solute to crystallize out of the solution, but it will not cause massive crystallization as the solution is already at its maximum solubility. Adding more water will not cause massive crystallization either as it will only dilute the solution and decrease the concentration of the solute.

Question 18

A 0.100 m solution of which one of the following solutes will have the lowest vapor pressure? A) Ca(ClO₄)₂ B) Al(ClO₄)₃ C) KClO₄ D) sucrose E) NaCl

Accepted Answer

Al(ClO4)3 dissociates into the most ions (4 ions: Al^3+ and 3 ClO4^-), leading to the greatest reduction in vapor pressure due to the colligative property effect.

Question 19

The Henry's law constant for helium gas in water at 30 °C is 3.70 × 10^-⁴M/atm. When the partial pressure of helium above a sample of water is 0.650 atm, the concentration of helium in the water is M A) 1.76 × 10³ B) 2.41 × 10^-⁴ C) 5.69 × 10^-⁴ D) 3.70 × 10^-⁴ E) 1.30

Accepted Answer

The concentration of helium in water can be calculated using Henry's law: C = kP, where C is the concentration, k is the Henry's law constant, and P is the partial pressure. Substituting the given values: C = (3.70 × 10^-4 M/atm) × (0.650 atm) = 2.41 × 10^-4 M.

Question 20

Which one of the following is most soluble in hexane (C₆H₁₄)? A) CH₃CH₂CH₂OH B) CH₃OH C) CH₃CH₂CH₂CH₂CH₂OH D) CH₃CH₂CH₂CH₂OH E) CH₃CH₂OH

Accepted Answer

The answer of Which one of the following is most...

Quiz 13: Properties of Solutions

Which of the following liquids will have the lowest freezing point?

A solution is prepared by dissolving calcium chloride in water and diluting to 500.0 mL. If this solution contains 44 ppm chloride ions, the concentration of calcium ions is ppm.

A supersaturated solution _ _.

The dissolution of water in octane (C₈H₁₈) is prevented by _ _.

When solutions of strong electrolytes in water are formed, the ions are surrounded by water molecules. These interactions are best described as a case of _.

The dissolution of gases in water is virtually always exothermic because _.

Which of the following is not a colloid?

A solution is prepared by adding 30.00 g of lactose (milk sugar) to 110.0 g of water at 55 °C. The partial pressure of water above the solution is torr. The vapor pressure of pure water at 55 °C is 118 torr. The MW of lactose is 342.3 g/mol.

An unsaturated solution is one that _.

Ammonium nitrate (NH₄NO₃) dissolves readily in water even though the dissolution is endothermic by 26.4 kJ/mol. The solution process is spontaneous because _.

A solution contains 28% phosphoric acid by mass. This means that .

Which of the following cannot be a colloid?

Calculate the freezing point of a solution containing 40.0 grams of KCl and 4400.0 grams of water. The molal- freezing- point- depression constant (K_f) for water is 1.86 ° C/m.

When argon is placed in a container of neon, the argon spontaneously disperses throughout the neon because .

A saturated solution .

The phrase "like dissolves like" refers to the fact that _.

In a saturated solution of a salt in water, .

A 0.100 m solution of which one of the following solutes will have the lowest vapor pressure?

The Henry's law constant for helium gas in water at 30 °C is 3.70 × 10^-⁴M/atm. When the partial pressure of helium above a sample of water is 0.650 atm, the concentration of helium in the water is M

Which one of the following is most soluble in hexane (C₆H₁₄) ?