Question 1

Which of the following aqueous solutions has the lowest freezing point?

Accepted Answer

Aluminum perchlorate, Al(ClO4)3, dissociates into four ions (one Al3+ and three ClO4-), which has the highest van't Hoff factor (i = 4) among the options. The freezing point depression is directly proportional to the van't Hoff factor and the molality of the solution, making the solution with aluminum perchlorate have the lowest freezing point.

Question 2

Which of the following is an example of a colloid?

Accepted Answer

Whipped cream is an example of a colloid because it consists of small droplets of fat dispersed throughout a water-based solution, creating a heterogeneous mixture. A colloid is defined as a mixture in which one substance is dispersed evenly throughout another substance. The other choices do not fit the definition of a colloid.

Question 3

Which of the following aqueous solutions has the highest boiling point?

Accepted Answer

The answer of Which of the following aqueous solutions has...

Question 4

Solutions are made that contain 0.10 moles of each of the following compounds in 100 g of H₂O. Choose the compound whose solution will have the highest freezing point.

Accepted Answer

The freezing point depression is determined by the number of particles in solution. NaI dissociates into 2 ions (Na⁺ and I^-), which is fewer than the other compounds, resulting in the least depression of the freezing point and thus the highest freezing point.

Question 5

Which of the following is a true solution with particles less than 1 nm in size?

Accepted Answer

Option A, calcium chloride in water, is a true solution with particles less than 1 nm in size. Calcium chloride is an ionic compound that readily dissolves in water, forming ions smaller than 1 nm. 
Option B, oil in water, is a colloidal solution with particles ranging in size from 1 nm to 1000 nm. 
Option C, whipped cream, is a foam and not a true solution because it has gas bubbles dispersed in a liquid. The size of these gas bubbles is usually larger than 1 nm. 
Option D, milk, is a colloidal mixture consisting of suspended particles ranging in size from 1 nm to several microns.

Question 6

Colligative properties are similar in that they all:

Accepted Answer

Colligative properties depend on the number of solute particles in solution, specifically the concentration of the solution. They do not depend on the chemical interactions between the solvent and solute, the nature of the solvent, or the presence of colloids.

Question 7

85.0 grams of potassium bromide are to be used to produce a 0.300 M solution. What will be the total volume of this solution?

Accepted Answer

To find the total volume of the solution, first calculate the number of moles of potassium bromide (KBr). The molar mass of KBr is approximately 119 g/mol (39 for K and 80 for Br). $$ \text{Moles of KBr} = \frac{85.0 \text{ g}}{119 \text{ g/mol}} \approx 0.714 \text{ moles} $$Given the concentration (Molarity, M) is 0.300 M, use the formula:$$ \text{Volume} = \frac{\text{Moles of solute}}{\text{Molarity}} = \frac{0.714}{0.300} $$$$ \text{Volume} \approx 2.38 \text{ L} $$Therefore, the total volume of the solution is approximately 2.38 L.

Question 8

Moles of solute per mole of solution is a definition of ________.

Accepted Answer

Mole fraction is defined as the ratio of the number of moles of a solute to the total number of moles of the solution.

Question 9

Solutions are made that contain 0.1 moles of each of the following compounds below in 100 g of H₂O. Choose the compound whose solution will have the lowest freezing point.

Accepted Answer

The freezing point depression is determined by the van't Hoff factor (i), which is the number of particles the compound dissociates into in solution. MgCl₂ dissociates into 3 ions (1 Mg²⁺ and 2 Cl^-), which is the highest among the given compounds, leading to the greatest freezing point depression.

Question 10

Moles of solute per liter of solution is the definition of ________.

Accepted Answer

Molarity is defined as the number of moles of solute dissolved per liter of solution. Molality is defined as the number of moles of solute dissolved per kilogram of solvent. Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature and pressure. Normality is a measure of concentration based on chemical equivalents rather than moles. Mole fraction is the ratio of moles of one component of a mixture to the total number of moles in the mixture.

Question 11

A solution containing 3.24 g of sulfur in 40 g of benzene boils 0.81°C above the boiling point of pure benzene. Determine the number of S atoms in one molecule of dissolved sulfur. Kb for benzene is 2.53°C m-1.

Accepted Answer

The answer of A solution containing 3.24 g of sulfur...

Question 12

Which of the following is a non-colligative property?

Accepted Answer

Solubility is not a colligative property. Colligative properties depend only on the number of solute particles present in a solution and not on their chemical identity. Solubility, on the other hand, depends on the specific chemical nature of the solute and solvent and is not related to the number of particles present.

Question 13

We wish to lower the freezing point of the water in an automobile radiator to -40°C. The total mass of water present is 12.0 kg. For which one of the following compounds would we have to use the greatest mass of solute to achieve this? You may assume that Kf for water = -1.86°C/m and that all ionizable solutes are completely ionized with unit activity even at this high concentration.

Accepted Answer

The answer of We wish to lower the freezing point...

Question 14

An aqueous solution contains 64.0 g of ethanol (C₂H₅OH) in 122.0 g of solution. What is the mole fraction of ethanol in the solution?

Accepted Answer

To find the mole fraction of ethanol, first calculate the moles of ethanol: 64.0 g / 46.08 g/mol = 1.39 mol. The mass of water is 122.0 g - 64.0 g = 58.0 g, and the moles of water are 58.0 g / 18.02 g/mol = 3.22 mol. The mole fraction of ethanol is 1.39 mol / (1.39 mol + 3.22 mol) = 0.301.

Question 15

Choose the correct statement.

Accepted Answer

A true colloidal particle will not settle out of the dispersing membrane due to the Brownian motion. Option A is incorrect because colloids are heterogeneous mixtures. Option C is incorrect because colloidal particles are usually unable to pass through semipermeable membranes. Option D is incorrect because electrolytes can affect the stability of colloids but are not protective colloids. Option E is incorrect because dispersion is one of the methods used to prepare colloids from larger particles, not from ions or molecules.

Question 16

A solution component present in lesser quantity than the solvent is called ________.

Accepted Answer

A solute is a substance that is present in a lesser quantity than the solvent in a solution. Options A, B, C, and E do not fit the definition of a solute.

Question 17

Which of the following combination of dispersed phase in a dispersion medium with the colloid type is INCORRECT?

Accepted Answer

Liquid in solid is not a type of colloidal system, therefore the combination of dispersed phase in a dispersion medium as "liquid in solid" is incorrect.

Question 18

Arrange the following three water solutions (all 250 cm3 in volume) according to decreasing osmotic pressure at 273 K: 5 g of C₂H₅OH, 5 g C₆H₁₂O₆ ,and 5 g C₁₂H₂₂O₁₁.

Accepted Answer

The osmotic pressure of a solution is directly proportional to the concentration of solute particles in the solution. The more solute particles a solution contains, the lower its water potential, and the higher its osmotic pressure. All three solutions have the same volume and contain the same type of solute, but differ in the number of solute particles. Among the given compounds, C₂H₅OH has the smallest molecular formula, and hence the lowest number of solute particles. On the other hand, C₁₂H₂₂O₁₁ has the largest molecular formula among the given compounds, and hence the highest number of solute particles. Therefore, the correct order from highest to lowest osmotic pressure is C₂H₅OH > C₆H₁₂O₆ > C₁₂H₂₂O₁₁.

Question 19

Which of the following material-colloid type combinations is INCORRECT?

Accepted Answer

The answer of Which of the following material-colloid type combinations...

Question 20

Choose the INCORRECT statement.

Accepted Answer

Colloidal particles are actually charged due to the adsorption of ions or charged molecules on their surface.

Quiz 13: Solutions and Their Physical Properties