1.
A water solution containing an unknown quantity of a nonelectrolyte solute has a freezing point of -0.665ºC. What is the molal concentration of the solution if Kf = -1.86ºC/m?
Correct Answer
B. .358
Explanation
none
2.
Colligative properties depend on
Correct Answer
A. The concentration of the solute particles.
Explanation
Colligative properties, such as boiling point elevation and freezing point depression, depend on the concentration of the solute particles. These properties are not affected by the identity of the solute particles or their physical properties. The concentration of the solute particles determines the extent to which the solute particles disrupt the solvent's normal behavior, leading to changes in the boiling and freezing points of the solution.
3.
A water solution containing an unknown quantity of a nonelectrolyte solute has a freezing point of -0.21ºC. What is the molal concentration of the solution if Kf = -1.86ºC/m?
Correct Answer
B. .11 m
Explanation
The freezing point depression is given as -0.21°C, and the cryoscopic constant (Kf) is given as -1.86°C/m. The molal concentration of the solution can be calculated using the formula ΔT = Kf * m, where ΔT is the freezing point depression and m is the molal concentration. Rearranging the formula, we get m = ΔT / Kf. Substituting the given values, we get m = -0.21°C / -1.86°C/m = 0.11 m. Therefore, the molal concentration of the solution is 0.11 m.
4.
The attraction of water molecules overcomes the strength of covalent bonds in
Correct Answer
A. Molecular substances that are electrolytes.
Explanation
In molecular substances that are electrolytes, the attraction of water molecules is strong enough to break the covalent bonds within the molecules. This allows the molecules to dissociate into ions, which can conduct electricity. In contrast, molecular substances that are not electrolytes do not dissociate into ions in water, so the attraction of water molecules does not overcome the strength of the covalent bonds. Therefore, the correct answer is molecular substances that are electrolytes.
5.
Electrolytes affect colligative properties differently than do nonelectrolytes because electrolytes
Correct Answer
A. Produce more moles of solute particles per mole of solute.
Explanation
Electrolytes affect colligative properties differently than nonelectrolytes because they produce more moles of solute particles per mole of solute. This is due to the fact that electrolytes dissociate into ions when dissolved in a solvent, while nonelectrolytes do not dissociate. The presence of more solute particles leads to a greater effect on colligative properties such as boiling point elevation, freezing point depression, and osmotic pressure.
6.
How many milliliters water are needed to make a 0.171 M solution that contains 1.00 g of NaCl?
Correct Answer
B. 100 mL
Explanation
To calculate the volume of water needed to make a 0.171 M solution with 1.00 g of NaCl, we need to use the formula Molarity = moles of solute / volume of solution in liters. First, we need to convert the mass of NaCl to moles by dividing it by its molar mass. The molar mass of NaCl is 58.44 g/mol. Therefore, 1.00 g of NaCl is equal to 1.00 / 58.44 = 0.0171 mol. Next, we rearrange the formula to solve for volume: volume = moles of solute / Molarity. Plugging in the values, we get volume = 0.0171 mol / 0.171 M = 0.1 L. Since 1 L is equal to 1000 mL, the volume needed is 0.1 L * 1000 mL/L = 100 mL.
7.
What is the molality of a solution that contains 5.10 mol KNO3 in 4.47 kg water?
Correct Answer
C. 1.14 m
Explanation
The molality of a solution is defined as the number of moles of solute per kilogram of solvent. In this question, the solute is KNO3 and the solvent is water. The question provides the number of moles of KNO3 (5.10 mol) and the mass of water (4.47 kg). To calculate molality, we divide the number of moles of KNO3 by the mass of water in kilograms. Therefore, the molality is 5.10 mol / 4.47 kg = 1.14 m.
8.
A solution containing a solute that dissolves as molecules; therefore, the solution does not conduct electricity
Correct Answer
A. Solute
Explanation
A solute is the substance that is being dissolved in a solution. In this context, the explanation suggests that the solution contains a solute that dissolves as molecules. When a solute dissolves as molecules, it means that the solute does not break apart into ions, which are necessary for conducting electricity. Therefore, the solution does not conduct electricity.
9.
A solution holding less than the maximum possible amount of solute under the solution conditions
Correct Answer
B. Unsaturated solution
Explanation
An unsaturated solution is a solution that can dissolve more solute under the given solution conditions. In other words, it holds less than the maximum possible amount of solute. This means that there is room for more solute to be dissolved in the solution.
10.
A concentrated form in which solutions are often stored
Correct Answer
C. Stock solution
Explanation
A stock solution is a concentrated form in which solutions are often stored. It is a solution that is prepared at a higher concentration than what is needed for immediate use. Stock solutions are commonly used in laboratories and industries where precise and accurate measurements are required. They allow for easy and convenient dilution to obtain the desired concentration for specific experiments or applications.
11.
This selectively allows some substances to pass through but not others
Correct Answer
B. Semipermeable membrane
Explanation
A semipermeable membrane is a type of membrane that allows only certain substances to pass through while blocking others. This property is due to the membrane's structure, which has small pores or channels that are selective in what they allow to pass. This allows for the separation or filtration of substances based on their size, charge, or other characteristics. Henry's Law, on the other hand, relates to the solubility of gases in liquids and is not directly related to the selective permeability of a membrane.
12.
A technique used to purify a solid; involves dissolving the solid in a solvent at high temperature, creating a saturated solution, then cooling the solution to cause the crystallization of the solid
Correct Answer
D. Recrystallization
Explanation
Recrystallization is a technique used to purify a solid by dissolving it in a solvent at high temperature, creating a saturated solution. When the solution is cooled, the solid crystallizes out, leaving impurities behind in the solution. This process allows for the removal of impurities and the isolation of a pure solid.
13.
The pressure produced on the surface of a semipermeable membrane by osmosis or the pressure required to stop osmotic flow
Correct Answer
C. Osmotic Pressure
Explanation
Osmotic pressure is the correct answer because it refers to the pressure produced on the surface of a semipermeable membrane by osmosis or the pressure required to stop osmotic flow. Osmosis is the process by which solvent molecules pass through a semipermeable membrane from a less concentrated solution to a more concentrated solution. The pressure exerted during this process is called osmotic pressure. Solvent and solute are related terms but do not specifically refer to the pressure produced by osmosis.
14.
The flow of solvent from a lower-concentration solution through a semipermeable membrane to a higher-concentration solution
Correct Answer
B. Osmosis
Explanation
Osmosis is the process in which solvent molecules move from an area of lower concentration to an area of higher concentration through a semipermeable membrane. In this case, the solvent is flowing from a lower-concentration solution to a higher-concentration solution, which is characteristic of osmosis. The movement of solute molecules is not mentioned in the question, and the term "membranes" is too broad to be the correct answer. Therefore, the correct answer is osmosis.
15.
A solution holding more than the normal maximum amount of solute
Correct Answer
B. Supersaturated solution
Explanation
A supersaturated solution is a solution that contains more solute than it can normally hold at a given temperature. This can be achieved by dissolving the solute in a solvent at a higher temperature and then cooling it down slowly, allowing the excess solute to remain dissolved. As a result, the solution becomes unstable and any disturbance or addition of a seed crystal can cause the excess solute to crystallize out.
16.
Physical properties of solutions that depend on the number of solute particles present but not the type of solute particles
Correct Answer
A. Colligative properties
Explanation
Colligative properties are physical properties of solutions that depend on the number of solute particles present but not the type of solute particles. These properties include boiling point elevation, freezing point depression, osmotic pressure, and vapor pressure lowering. They are directly proportional to the concentration of the solute particles and are independent of the chemical nature of the solute.
17.
If the amount of solute present in a solution at a given temperature is less than the maximum amount that can dissolve at that temperature, the solution is said to be
Correct Answer
D. Unsaturated.
Explanation
If the amount of solute present in a solution at a given temperature is less than the maximum amount that can dissolve at that temperature, the solution is said to be unsaturated. This means that there is still room for more solute to dissolve in the solution.
18.
As temperature increases, solubility of gases in liquids
Correct Answer
A. Decreases
Explanation
As temperature increases, the solubility of gases in liquids generally decreases. This is because higher temperatures provide more energy to the gas molecules, causing them to move faster and escape from the liquid more easily. This reduces the amount of gas that can dissolve in the liquid, leading to a decrease in solubility.
19.
The rate of dissolution is
Correct Answer
B. Not related to solubility.
Explanation
The rate of dissolution refers to how quickly a solute dissolves in a solvent. It is not related to the solubility of the solute, which is the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature and pressure. The rate of dissolution can be influenced by factors such as temperature, surface area, and stirring, but not by the solubility of the solute.
20.
Which of the following will dissolve most slowly?
Correct Answer
C. Large salt crystals in unstirred water
Explanation
Large salt crystals in unstirred water will dissolve most slowly because the rate of dissolution depends on the surface area of the solute exposed to the solvent. In this case, the large salt crystals have a smaller surface area compared to the small salt crystals. Additionally, stirring the water increases the contact between the solute and solvent, thus increasing the rate of dissolution. Therefore, the combination of large salt crystals and unstirred water results in the slowest dissolution rate.
21.
A substance whose water solution conducts a current is a(n)
Correct Answer
A. Electrolyte.
Explanation
An electrolyte is a substance that, when dissolved in water, dissociates into ions and allows the flow of electric current. This is why a water solution of an electrolyte conducts a current. In contrast, solute refers to any substance that is dissolved in a solution, regardless of its ability to conduct electricity. Nonpolar substances, on the other hand, do not dissociate into ions and therefore do not conduct a current in water. Nonelectrolyte refers to a substance that does not dissociate into ions and does not conduct electricity in water.
22.
Which of the following is expressed in grams of solute instead of moles of solute?
Correct Answer
D. Neither
Explanation
The question is asking which of the options is expressed in grams of solute instead of moles of solute. Molality and molarity are both expressed in moles of solute, not grams. Therefore, the correct answer is "neither" because none of the options are expressed in grams of solute.
23.
Which of the following is a thoroughly mixed homogeneous mixture of substances in a single phase?
Correct Answer
C. A solution
Explanation
A solution is a thoroughly mixed homogeneous mixture of substances in a single phase. In a solution, the solute particles are evenly distributed and cannot be easily separated from the solvent. This is different from a suspension, where the solute particles are not evenly distributed and can settle over time. A colloid is also a homogeneous mixture, but the solute particles are larger than those in a solution and do not settle. A compound, on the other hand, is a substance formed by the chemical combination of two or more elements.
24.
Which of the following is an example of a polar solvent?
Correct Answer
B. Water
Explanation
Water is an example of a polar solvent because it has a polar molecular structure. The oxygen atom in water is more electronegative than the hydrogen atoms, causing the electrons to spend more time around the oxygen atom. This creates a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms, resulting in a polar molecule. Polar solvents dissolve polar solutes, as the partial charges in the solvent can interact with the charges in the solute, allowing them to mix and form a solution.
25.
Which of the following is a homogeneous mixture?
Correct Answer
C. a sugar-water solution
Explanation
A homogeneous mixture is a mixture where the components are evenly distributed throughout, resulting in a uniform composition. In the case of a sugar-water solution, the sugar molecules are evenly dispersed in the water molecules, creating a uniform mixture. This makes the sugar-water solution a homogeneous mixture. Whole-wheat bread is not a homogeneous mixture as it contains different components like flour, water, yeast, etc. Sugar is also not a homogeneous mixture as it consists of individual sugar crystals. Water, on its own, is a pure substance and not a mixture.