Question 1

Which of the following best explains why noncovalent interactions are critical for the structure and function of biomolecules?

Accepted Answer

Noncovalent interactions are weak and reversible, allowing biomolecules to dynamically interact and respond to environmental changes.

Question 2

Given the following bond energies, which type of noncovalent interaction is generally the weakest in biomolecules?

Accepted Answer

Van der Waals interaction (0.4–0.8 kJ/mol)

Question 3

Which of the following molecules is most likely to form hydrogen bonds with water?

Accepted Answer

Ethanol ($$CH_3CH_2OH)$$

Question 4

Water has a high boiling point compared to other small molecules. Which property of water is primarily responsible for this?

Accepted Answer

Its ability to form multiple hydrogen bonds due to its tetrahedral geometry

Question 5

A solution contains 0.1 M acetic acid ($$K_a = 1.76 	imes 10$$^{-5}$$). What is the approximate pH of this solution?

Accepted Answer

$$pH \approx 4.75$$

Question 6

Which of the following statements about amphipathic molecules is correct?

Accepted Answer

They contain both hydrophilic and hydrophobic regions, allowing them to form micelles or bilayers in water.

Question 7

What is the pH of pure water at 25°C, given $$K_w = 1.0 	imes 10$$^{-14}$$?

Accepted Answer

$$pH = 7$$

Question 8

Which equation correctly relates pH, pOH, and $$K_w in $$aqueous solution at 25°C?

Accepted Answer

$$pH + pOH = 14$$

Question 9

A buffer solution is prepared by mixing 0.025 M acetic acid and 0.005 M sodium acetate. What is the pH of the solution? ($$pK_a = 4.75)$$

Accepted Answer

$$pH = 4.75 + \log\left(\frac{0.005}{0.025}\right)$$

Question 10

Which of the following best describes the hydrophobic effect?

Accepted Answer

The exclusion of nonpolar substances from water, resulting in increased entropy of water molecules.

Question 11

Which of the following is TRUE regarding the isoelectric point (pI) of glycine?

Accepted Answer

It is the average of the two pK values surrounding the neutral species.

Question 12

Which property of water allows it to dissolve ionic compounds such as NaCl?

Accepted Answer

Its high dielectric constant

Question 13

A student adds 10 μL of 1 M HCl to 1 L of pure water. What will happen to the pH?

Accepted Answer

The pH will decrease by approximately 2 units.

Question 14

Which of the following statements about hydrogen bonds in biological molecules is correct?

Accepted Answer

Hydrogen bonds can form between water and other functional groups such as alcohols and amines.

Question 15

At pH 7.0, which phosphate species predominates in solution, given $$pK_2 = 7.2$ for H_2PO_4$$^-$$?

Accepted Answer

$$H_2PO_4^-$$

Question 16

Which of the following best describes the effect of increasing ionic strength on macroion interactions in solution?

Accepted Answer

It shields the charge interactions, reducing attraction and repulsion between macroions.

Question 17

Which equation is used to calculate the pH of a buffer solution containing a weak acid and its conjugate base?

Accepted Answer

$$pH = pK_a + \log\left(\frac{[A^-]}{[HA]}\right)$$

Question 18

Which of the following is a consequence of water’s ability to form four hydrogen bonds per molecule?

Accepted Answer

Water has a high surface tension and boiling point.

Question 19

A solution contains both $$H_2CO_3$$ and $$HCO_3$$^-$$. Which physiological system uses this buffer to regulate pH?

Accepted Answer

Blood (carbonic acid/bicarbonate buffer)

Aqueous Chemistry: Water – Structure, Interactions, and Properties

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