Q: A solution has a pH of 3. What is the hydrogen ion concentration $$[H^+] in $$this solution?

$$[H^+] = 1 \times 10$$^{-3}$$\ \mathrm{M}$$

Question 1

Which property of water is primarily responsible for the ability of ice to float on liquid water, and what is the molecular explanation for this phenomenon?

Accepted Answer

Water's expansion upon freezing; hydrogen bonds form a crystalline lattice that spaces molecules farther apart in ice than in liquid water.

Question 2

A scientist is studying a solution with a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-5}$$\ \mathrm{M}. $$What is the pH of this solution?

Accepted Answer

$$pH = 5$$

Question 3

Which of the following best explains why water is an effective solvent for ionic and polar substances?

Accepted Answer

Water's polarity allows it to surround and interact with charged and partially charged regions of solutes, forming hydration shells.

Question 4

A beaker contains 1 liter of a 0.1 M NaOH solution. What is the concentration of hydroxide ions $$[OH^-] in $$the solution?

Accepted Answer

$$[OH^-] = 0.1\ \mathrm{M}$$

Question 5

Which of the following scenarios best illustrates the concept of evaporative cooling in a biological context?

Accepted Answer

A human sweating during exercise, where the evaporation of sweat cools the skin.

Question 6

If the pH of blood drops from 7.4 to 7.2, what happens to the hydrogen ion concentration $$[H^+]$$?

Accepted Answer

$$[H^+]$$ increases by a factor of 2

Question 7

Which of the following best describes a buffer and its function in biological systems?

Accepted Answer

A buffer is a substance that minimizes changes in pH by reversibly accepting or donating hydrogen ions.

Question 8

A solution has a pH of 3. What is the hydrogen ion concentration $$[H^+] in $$this solution?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-3}$$\ \mathrm{M}$$

Question 9

Which of the following statements about hydrophobic substances is correct?

Accepted Answer

Hydrophobic substances have mostly nonpolar bonds and do not mix well with water.

Question 10

A marine biologist is concerned about ocean acidification. Which chemical reaction best represents the process by which increased atmospheric $$CO_2$$ leads to a decrease in carbonate ion concentration in seawater?

Accepted Answer

$$CO_2 + H_2O$$ \rightarrow H_2CO_3 \rightarrow $$HCO_3^- + H$$^+$$; then H$$^+ + $$CO_3$$^{2-} \rightarrow $$HCO_3$$^-$$

Question 11

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

Accepted Answer

Hydrogen bonds between water molecules require a large amount of energy to break, so water resists temperature changes.

Question 12

A student adds 1 mole of glucose (molecular mass = 180 g/mol) to enough water to make 1 liter of solution. What is the molarity of the solution?

Accepted Answer

1 M

Question 13

Which of the following is a real-life consequence if ice were denser than liquid water?

Accepted Answer

Ice would sink, causing lakes and oceans to freeze solid, threatening aquatic life.

Question 14

Which of the following best describes the relationship between pH and hydrogen ion concentration $$[H^+]$$?

Accepted Answer

$$pH = -\log [H^+]$$

Question 15

A solution has a pH of 8. What is the hydroxide ion concentration $$[OH^-] at 25$$°C?

Accepted Answer

$$[OH^-] = 1 	imes 10$$^{-6}$$\ \mathrm{M}$$

Question 16

Which of the following best explains why water is considered a polar molecule?

Accepted Answer

The oxygen atom is more electronegative than hydrogen, resulting in an uneven distribution of charge.

Question 17

Which of the following is an example of a hydrophilic substance?

Accepted Answer

Table salt (NaCl)

Question 18

A weak acid, such as acetic acid ($$CH_3COOH$$), is added to water. Which statement best describes its behavior?

Accepted Answer

It reversibly releases and accepts hydrogen ions, partially dissociating in water.

Question 19

Which of the following best describes the role of buffers in blood serum?

Accepted Answer

Buffers minimize changes in blood pH by reversibly binding or releasing hydrogen ions.

Water and Life: Properties, Structure, and Biological Importance

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