Question 1

The shape of a protein molecule is determined completely by
A) hydrogen bonding.
B) ion-dipole attractions.
C) dispersion forces.
D) disulfide bridges.
E) the sequence of amino acids in the chain.

Accepted Answer

The sequence of amino acids in the protein chain determines the folding and shape of the protein molecule. This process is known as protein folding, and it is essential to the protein's function. The specific sequence of amino acids creates a unique pattern of hydrogen bonding, ionic interactions, and van der Waals forces that cause the protein to fold into a specific shape. Disulfide bridges do play a role in protein folding, but they are not solely responsible for determining the shape of the protein molecule.

Question 2

Potassium fluoride is used for frosting glass. Calculate the molarity of a solution prepared by dissolving 78.6 g of KF in enough water to produce 225 mL of solution.
A) 0.304 M
B) 0.349 M
C) 1.35 M
D) 3.29 M
E) 6.01 M

Accepted Answer

E

Question 3

Which of the following sets of conditions could exist when two liquids which are completely miscible in one another are mixed? A) ?H_soln > 0, entropy of system decreases B) ?H_soln $\approx$ 0, entropy of system decreases C) ?H_soln $\approx$ 0, entropy change of system $\approx$ 0 D) ?H_soln $\approx$ 0, entropy of system increases E) None of these choices is correct.

Accepted Answer

When two liquids are completely miscible, they mix uniformly and the molecules become more disordered, leading to an increase in the entropy of the system. Therefore, the Gibbs free energy change (∆G) of the solution is negative, which corresponds to a favorable, spontaneous process. This means that ∆H (enthalpy change) of the solution must be negative (exothermic) to compensate for the positive ∆S (entropy change). Thus, choice D is the correct option, where both ∆H and ∆S are positive, indicating an increase in the entropy of the system.

Question 4

Consider the expression below, showing the terms which contribute to the heat of solution, ∆H_soln: ∆H_soln = ∆H_solute + ∆H_solvent + ∆H_mix Which of the following sets correctly shows the signs (positive or negative) of the three terms on the right hand side of the equation? A) ∆H_solute > 0; ∆H_solvent > 0; ∆H_mix > 0 B) ∆H_solute <0; ∆H_solvent < 0; ∆H_mix < 0 C) ∆H_solute > 0; ∆H_solvent > 0; ∆H_mix < 0 D) ∆H_solute < 0; ∆H_solvent < 0; ∆H_mix > 0 E) ∆H_solute < 0; ∆H_solvent > 0; ∆H_mix < 0

Accepted Answer

∆H_solute > 0 since the dissolving process of a solid solute requires energy to overcome attractive forces among the solute particles. ∆H_solvent > 0 since the solvation process of a solvent requires energy to overcome attractive forces among the solvent particles. ∆H_mix < 0 since the mixing process involves the breaking of some solute-solute and solvent-solvent interactions and the formation of new solute-solvent interactions. The net effect is often a decrease in energy.

Question 5

Soda drinks bubble when the bottle is opened because
A) the temperature of the soda increases.
B) exposure to atmospheric pressure squeezes the carbon dioxide from solution.
C) the partial pressure of carbon dioxide above the solution is reduced.
D) atmospheric nitrogen molecules displace carbon dioxide molecules.
E) the Henry's law constant changes due to the change in pressure.

Accepted Answer

The answer of Soda drinks bubble when the bottle is...

Question 6

A solution of sucrose (sugar) in water is in equilibrium with solid sucrose. If more solid sucrose is now added, with stirring,
A) the concentration of the solution will increase.
B) the concentration of the solution will decrease.
C) the concentration of the solution will remain the same.
D) the volume of solution will increase.
E) a supersaturated solution will be produced.

Accepted Answer

According to Le Chatelier's Principle, when more solid sucrose is added, the system will try to shift the equilibrium to the left to maintain the equilibrium constant. This means that some of the sugar in the solution will precipitate out to form solid sucrose, and the concentration of the solution will remain the same.

Question 7

Which of the following pairs of ions is arranged so that the ion with the smaller charge density is listed first? A) K⁺, Rb⁺ B) Cl^¯, K⁺ C) Cl^¯, Br^¯ D) Ca²⁺, Ba²⁺ E) None of these pairs are arranged in this way.

Accepted Answer

In an ion pair, the charge density increases with the magnitude of the charge and decreases with the size of the ion. Therefore, in the pair Cl¯ and K+, the Cl¯ ion has a larger charge density than K+. Similarly, in the pair Cl¯ and Br¯, the Cl¯ ion has a smaller size and larger charge density than Br¯. Therefore, the pair Cl¯ and K+ in option B is arranged so that the ion with smaller charge density (K+) is listed first.

Question 8

The Henry's Law constant (k) for carbon monoxide in water at 25$\degree$C is 9.71 *10^¯⁴ mol/(L·atm). How many grams of CO will dissolve in 1.00 L of water if the partial pressure of CO is 2.75 atm? A) 3.53 *10^¯⁴ g B) 2.67 * 10^¯³ g C) 9.89 *10^¯³ g D) 7.48 * 10^¯² g E) None of these choices is correct.

Accepted Answer

The answer of The Henry's Law constant (k) for carbon...

Question 9

Which of the following pairs of ions is arranged so that the ion with the larger (i.e., more negative) heat of hydration is listed first? A) Br^¯, K⁺ B) Mg²⁺, Sr ²⁺ C) Ca²⁺, Sc³⁺ D) Na⁺, Li⁺ E) None of these pairs are arranged in this way.

Accepted Answer

Mg²⁺ has a more negative heat of hydration than Sr²⁺ due to its smaller size and higher charge density.

Question 10

Which of the following ions will be expected to have the most negative heat of hydration, ∆H_hydr? A) Na⁺ B) Cs⁺ C) Ca²⁺ D) F^¯ E) I^¯

Accepted Answer

The answer of Which of the following ions will be...

Question 11

Select the type of interaction which best describes the attraction between Mg²⁺ ions and water molecules. A) dipole-dipole B) dipole-induced dipole C) ion-dipole D) ion-induced dipole E) ion-hydrogen bond

Accepted Answer

Mg²⁺ ions have a strong positive and negative charge, making them highly polar. Water molecules are also polar, with a partially positive hydrogen end and a partially negative oxygen end. The strong attraction between the polar Mg²⁺ ions and water molecules is due to ion-dipole interactions.

Question 12

Methane has a Henry's Law constant (k) of 9.88 * 10² mol/(L·atm) when dissolved in benzene at 25$\degree$C. How many grams of CH₄ will dissolve in 3.00 L of benzene if the partial pressure of CH₄ is 1.48 atm? A) 0.0667 g B) 0.146 g C) 2.34 g D) 4.83 g E) 7.02 g

Accepted Answer

The answer of Methane has a Henry's Law constant (k)...

Question 13

A saturated solution of carbon dioxide in water contains 3.00 g of CO₂ when the CO₂ partial pressure is 8.0 atm. What mass of CO₂ will escape if the partial pressure is lowered to 3.2 atm? A) 0.90 g B) 1.20 g C) 1.40 g D) 1.80 g E) 2.20 g

Accepted Answer

The solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid, according to Henry's Law. When the pressure is reduced from 8.0 atm to 3.2 atm, it becomes 3.2/8.0 = 0.4 times its original pressure. Therefore, the new amount of CO2 that can remain dissolved in water is 3.00 g * 0.4 = 1.20 g. The mass of CO2 that will escape is the original mass minus the new mass, which is 3.00 g - 1.20 g = 1.80 g.

Question 14

The most abundant molecules in the cell membranes of most species are
A) proteins.
B) sugars.
C) phospholipids.
D) fatty acids.
E) steroids.

Accepted Answer

Phospholipids are the most abundant molecules in cell membranes. They form a bilayer that makes up the basic structure of the membrane. While proteins, sugars, fatty acids, and steroids are present in membranes, they are not as abundant as phospholipids.

Question 15

Based only on the relative lattice energies of the compounds below, which one would be expected to have the lowest solubility in water?
A) NaBr
B) CaS
C) NaOH
D) KI
E) CsCl

Accepted Answer

The compound with the highest lattice energy is expected to have the lowest solubility in water because it requires more energy to break apart the crystal lattice and dissolve in water. CaS has the highest lattice energy among the given compounds, while the others have lower lattice energies in the order NaOH > NaBr > KI > CsCl. Therefore, CaS would be expected to have the lowest solubility in water.

Question 16

Which, if any, of the following features is common to soaps, detergents, phospholipids and channel-forming antibiotics?
A) They all contain fatty acids.
B) They all contain phosphate groups.
C) They all contain polypeptide chains.
D) Their function depends on the dual polarity of their molecules.
E) They have none of these features in common.

Accepted Answer

All these substances have amphipathic properties, meaning they contain both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts, which is crucial for their function.

Question 17

Under physiological conditions, amino acids in solution carry A) no electrical charges. B) a net positive charge, due to an -NH₃⁺ group or groups. C) a net negative charge, due to a -COO^¯ group or groups. D) both -NH₂ and -COOH groups. E) both -NH₃⁺ and -COO^¯ groups.

Accepted Answer

Amino acids have both amino (-NH2) and carboxyl (-COOH) groups, which can ionize to form -NH3+ and -COO- groups, respectively, in solution. Therefore, amino acids in solution carry both positive and negative charges, making choice E the correct answer.

Question 18

For a given solution, which of the following concentration values will change as temperature changes?
A) mass percent
B) molality
C) mole fraction
D) molarity
E) None of these choices is correct.

Accepted Answer

Molarity is directly proportional to temperature, as the volume of solution changes with temperature. Therefore, molarity will change as temperature changes. The other concentration values listed are not affected by changes in temperature.

Question 19

If a solute dissolves in an endothermic process
A) H bonds must exist between solvent and solute.
B) strong ion-dipole forces must exist in the solution.
C) the solute must be a gas.
D) the entropy of the solution is immaterial.
E) the entropy of the solution must be greater than that of its pure components.

Accepted Answer

In an endothermic dissolution process, the system absorbs heat from the surroundings. For the process to be spontaneous, the increase in entropy (disorder) of the system (solution) must compensate for the absorbed heat, meaning the entropy of the solution must be greater than that of its pure components.

Question 20

When two pure substances are mixed to form a solution
A) heat is released.
B) heat is absorbed.
C) there is an increase in entropy.
D) there is a decrease in entropy.
E) entropy is conserved.

Accepted Answer

Mixing two pure substances typically leads to an increase in disorder or randomness in the system, which is an increase in entropy. This is because the individual molecules of each substance become more randomly distributed throughout the solution, increasing the number of possible arrangements of the particles in the system.

Quiz 13: The Properties of Mixtures: Solutions and Colloids

The shape of a protein molecule is determined completely by

Potassium fluoride is used for frosting glass. Calculate the molarity of a solution prepared by dissolving 78.6 g of KF in enough water to produce 225 mL of solution.

Which of the following sets of conditions could exist when two liquids which are completely miscible in one another are mixed?

Consider the expression below, showing the terms which contribute to the heat of solution, ∆H_soln: ∆H_soln = ∆H_solute + ∆H_solvent + ∆H_mix Which of the following sets correctly shows the signs (positive or negative) of the three terms on the right hand side of the equation?

Soda drinks bubble when the bottle is opened because

A solution of sucrose (sugar) in water is in equilibrium with solid sucrose. If more solid sucrose is now added, with stirring,

Which of the following pairs of ions is arranged so that the ion with the smaller charge density is listed first?

The Henry's Law constant (k) for carbon monoxide in water at 25 $\degree$ C is 9.71 *10^¯⁴ mol/(L·atm) . How many grams of CO will dissolve in 1.00 L of water if the partial pressure of CO is 2.75 atm?

Which of the following pairs of ions is arranged so that the ion with the larger (i.e., more negative) heat of hydration is listed first?

Which of the following ions will be expected to have the most negative heat of hydration, ∆H_hydr?

Select the type of interaction which best describes the attraction between Mg²⁺ ions and water molecules.

Methane has a Henry's Law constant (k) of 9.88 * 10² mol/(L·atm) when dissolved in benzene at 25 $\degree$ C. How many grams of CH₄ will dissolve in 3.00 L of benzene if the partial pressure of CH₄ is 1.48 atm?

A saturated solution of carbon dioxide in water contains 3.00 g of CO₂ when the CO₂ partial pressure is 8.0 atm. What mass of CO₂ will escape if the partial pressure is lowered to 3.2 atm?

The most abundant molecules in the cell membranes of most species are

Based only on the relative lattice energies of the compounds below, which one would be expected to have the lowest solubility in water?

Which, if any, of the following features is common to soaps, detergents, phospholipids and channel-forming antibiotics?

Under physiological conditions, amino acids in solution carry

For a given solution, which of the following concentration values will change as temperature changes?

If a solute dissolves in an endothermic process

When two pure substances are mixed to form a solution