Q: A solution has a pH of 5. What is the hydrogen ion concentration $$[H^+] in $$this solution?

$$[H^+] = 1 \times 10$$^{-5}$$ \ M$$

Question 1

Which property of water is primarily responsible for the ability of insects, such as water striders, to walk on the surface of a pond?

Accepted Answer

Cohesion due to hydrogen bonding

Question 2

A water molecule has a bent shape. Which statement best explains how this structure leads to water’s polarity?

Accepted Answer

The unequal sharing of electrons and bent shape create a partial negative charge near oxygen and partial positive charges near hydrogens.

Question 3

Which of the following best describes why ice floats on liquid water, and what is the ecological significance of this property?

Accepted Answer

Hydrogen bonds in ice are more stable and hold molecules further apart, making ice less dense than liquid water, allowing it to float and insulate aquatic environments.

Question 4

Which equation correctly relates the hydrogen ion concentration $$[H^+] to pH$$?

Accepted Answer

$$pH = -\log_{10}[H^+]$$

Question 5

A solution has a pH of 5. What is the hydrogen ion concentration $$[H^+] in $$this solution?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-5}$$ \ M$$

Question 6

Which of the following scenarios best illustrates the function of a buffer in a biological system?

Accepted Answer

A buffer absorbs excess hydrogen ions when acid is added, minimizing changes in pH.

Question 7

Which property of water allows it to moderate temperature in living organisms and environments?

Accepted Answer

High specific heat

Question 8

A lake remains liquid under a layer of ice during winter. Which combination of water’s properties is most responsible for this phenomenon?

Accepted Answer

High heat of vaporization and low density of ice

Question 9

If the pH of a solution changes from 7 to 4, how does the hydrogen ion concentration change?

Accepted Answer

It increases by 1,000 times

Question 10

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

Accepted Answer

Water’s polarity allows it to surround and separate ions and polar molecules through hydrogen bonding.

Question 11

A biologist adds a strong acid to a buffered solution and observes only a slight decrease in pH. What is the most likely explanation?

Accepted Answer

The buffer neutralizes added acid by binding free hydrogen ions.

Question 12

Which emergent property of water is most important for the transport of water from the roots to the leaves in plants?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 13

Which of the following best describes the relationship between water’s high heat of vaporization and its role in cooling living organisms?

Accepted Answer

Evaporation of water removes large amounts of heat from organisms, helping regulate body temperature.

Question 14

A solution has a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-9}$$ \ M. $$What is its pH?

Accepted Answer

$$pH = 9$$

Question 15

Which of the following is NOT a consequence of hydrogen bonding between water molecules?

Accepted Answer

Water’s nonpolar nature

Question 16

A patient’s blood pH drops from 7.4 to 7.0. Which statement best describes the role of buffers in this scenario?

Accepted Answer

Buffers would absorb excess hydrogen ions to minimize the pH change.

Question 17

Which of the following best explains why coastal regions tend to have milder climates than inland regions?

Accepted Answer

Water’s high specific heat allows it to absorb and release heat slowly, moderating temperature changes.

Question 18

Which of the following is a direct result of water’s ability to form hydrogen bonds?

Accepted Answer

Water has a high surface tension.

Question 19

A scientist adds a base to a solution, causing the pH to rise from 6 to 8. By what factor did the hydrogen ion concentration decrease?

Accepted Answer

100 times

Question 20

Which of the following best describes the effect of water’s expansion upon freezing on aquatic life during winter?

Accepted Answer

Ice floats, forming an insulating layer that protects aquatic life below from freezing temperatures.

Water and Its Role in Biological Systems; Acids, Bases, and Buffers

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