Question 1

Which of the following statements best explains why water has a high specific heat compared to other small molecules?

Accepted Answer

Water molecules form extensive hydrogen bonds, which require significant energy to break.

Question 2

Which of the following functional groups is most likely to act as a hydrogen bond donor in an aqueous environment?

Accepted Answer

Amino group ($$-\mathrm{NH}_2)$$

Question 3

A solution contains a weak acid with $$pK_a = 5.0. If $$the ratio of conjugate base to acid ($$[A^-]/[HA]) is 10$$, what is the pH of the solution? Use the Henderson-Hasselbalch equation.

Accepted Answer

$$pH = 6.0$$

Question 4

Which of the following best describes the hydrophobic effect?

Accepted Answer

The tendency of nonpolar molecules to aggregate in water, driven by increased entropy of water molecules.

Question 5

Which of the following statements about ionic interactions in aqueous solution is correct?

Accepted Answer

Ionic interactions are weakened in water due to its high dielectric constant.

Question 6

A peptide contains both acidic and basic side chains. At a pH equal to its isoelectric point ($$pI$$), which of the following is true?

Accepted Answer

The peptide has no net electric charge.

Question 7

Which of the following best describes a zwitterion?

Accepted Answer

A molecule with both positive and negative charges but an overall neutral charge.

Question 8

Which of the following functional groups is most likely to form a salt bridge at physiological pH?

Accepted Answer

Amino ($$-\mathrm{NH}_3^+) $$and carboxylate ($$-\mathrm{COO}^-) $$groups

Question 9

A solution is made by dissolving 0.01 M of a strong acid in water. What is the pH of the solution?

Accepted Answer

$$pH = 2$$

Question 10

Which of the following best explains why ice is less dense than liquid water?

Accepted Answer

Hydrogen bonding in ice forms an open, hexagonal lattice structure.

Question 11

Which of the following molecules is most likely to be amphipathic?

Accepted Answer

A phospholipid with a polar head and nonpolar tails

Question 12

Which of the following is a correct application of the Henderson-Hasselbalch equation?

Accepted Answer

Calculating the ratio of conjugate base to acid at a given pH for a weak acid.

Question 13

Which of the following best describes a hydration shell?

Accepted Answer

A layer of water molecules oriented around a charged or polar solute.

Question 14

Which of the following statements about van der Waals forces is correct?

Accepted Answer

They include both dipole-dipole and London dispersion interactions.

Question 15

A weak acid has a $$pK_a of 4.5. At $$what pH will the concentrations of acid and conjugate base be equal?

Accepted Answer

$$pH = 4.5$$

Question 16

Which of the following best describes the role of the carbonic acid/bicarbonate buffer system in blood?

Accepted Answer

It maintains blood pH by neutralizing excess acids or bases.

Question 17

Which of the following is a consequence of the high dielectric constant of water?

Accepted Answer

Water can dissolve many ionic compounds.

Question 18

A solution contains a polyprotic weak acid with $$pK_{a1} = 2.0$$ and $$pK_{a2} = 7.0. $$What is the isoelectric point ($$pI) of $$this acid?

Accepted Answer

$$pI = 4.5$$

Question 19

Which of the following best describes a micelle?

Accepted Answer

A spherical structure formed by amphipathic molecules in water, with hydrophobic tails inward and hydrophilic heads outward.

Question 20

Which of the following changes would most likely increase the solubility of a macroion in water?

Accepted Answer

Increasing the ionic strength of the solution, which enhances the counterion atmosphere.

Chapter 2: The Chemical Foundation of Life – Weak Interactions in an Aqueous Environment

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