$$ 1.0 \times 10^{-7} \ \mathrm{M} $$

Question 1

Which property of water is primarily responsible for its unusually high boiling point compared to other molecules of similar size?

Accepted Answer

Its extensive hydrogen bonding network

Question 2

Which of the following best explains why nonpolar gases such as O$$_2$$ and N$$_2$$ are poorly soluble in water?

Accepted Answer

They disrupt the hydrogen-bonded structure of water, which is energetically unfavorable

Question 3

What is the primary driving force for the formation of micelles by amphipathic molecules in water?

Accepted Answer

Maximizing the entropy of water molecules by minimizing the surface area of hydrophobic regions exposed to water

Question 4

Which equation correctly represents the ionization of water?

Accepted Answer

$$ \mathrm{2H_2O \rightleftharpoons H_3O^+ + OH^-} $$

Question 5

Given the ion product of water at 25$$^\circC is$$ $$K_w = 1.0 	imes 10$$^{-14}$$, what is the concentration of $$[H^+]$$ in pure water?

Accepted Answer

$$ 1.0 	imes 10^{-7} \ \mathrm{M} $$

Question 6

Which of the following best describes the effect of adding a nonvolatile solute to water?

Accepted Answer

It lowers the freezing point and raises the boiling point of water

Question 7

Which equation is used to calculate the pH of a solution?

Accepted Answer

$$ \mathrm{pH = -\log[H^+]} $$

Question 8

A buffer solution is prepared by mixing acetic acid and sodium acetate. Which equation would you use to calculate the pH of this buffer?

Accepted Answer

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

Question 9

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

Accepted Answer

Each water molecule can form up to four hydrogen bonds

Question 10

Which of the following best explains why water is an excellent solvent for ionic compounds?

Accepted Answer

Water's high dielectric constant reduces the electrostatic attraction between ions

Question 11

A solution contains $$[H^+] = 2.5 	imes 10$$^{-5}$$ M. What is the pH of this solution?

Accepted Answer

$$ 4.60 $$

Question 12

Which of the following is a correct statement about the titration curve of a weak acid?

Accepted Answer

The pH changes rapidly near the equivalence point

Question 13

Which of the following is the correct expression for the equilibrium constant for the ionization of a weak acid HA?

Accepted Answer

$$ K_a = \frac{[H^+][A^-]}{[HA]} $$

Question 14

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers prevent changes in pH when small amounts of acid or base are added

Question 15

Which of the following is a real-life example of a biological buffer system?

Accepted Answer

The phosphate buffer system in cytoplasm

Question 16

Which of the following equations represents the Henderson-Hasselbalch equation?

Accepted Answer

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

Question 17

Which of the following statements about the structure of ice is correct?

Accepted Answer

Ice has a lower density than liquid water due to its open hydrogen-bonded lattice

Question 18

Which of the following best explains why water is considered an amphoteric molecule?

Accepted Answer

It can act as both an acid and a base

Question 19

A patient’s blood pH is measured at 7.1. Which buffer system is primarily responsible for maintaining blood pH near 7.4?

Accepted Answer

Bicarbonate buffer system

Chapter 2: Water – Structure, Properties, and Biological Significance

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