$$[H^+] = 10$$^{-5}$$ \ \text{M}, \ pH = 5$$

Question 1

Which property of water allows a water strider to walk on the surface of a pond without sinking?

Accepted Answer

Surface tension

Question 2

Why is ice less dense than liquid water?

Accepted Answer

Hydrogen bonds in ice are more stable and hold water molecules further apart

Question 3

A solution has a hydrogen ion concentration of $$[H^+] = 10$$^{-4}$$ \ 	ext{M}. $$What is its pH?

Accepted Answer

$$pH = -\log_{10}(10$$^{-4}$$) = 4$$

Question 4

Which of the following best explains why NaCl dissolves readily in water?

Accepted Answer

Water molecules surround and stabilize Na+ and Cl- ions through ion-dipole interactions

Question 5

Which of the following molecules would be classified as amphipathic?

Accepted Answer

Phospholipid

Question 6

What is the primary reason water is essential for most chemical reactions in living organisms?

Accepted Answer

Water allows molecules to interact by dissolving them and facilitating collisions

Question 7

A patient’s blood pH drops from 7.4 to 7.0. What is the change in hydrogen ion concentration?

Accepted Answer

It increases by a factor of 4

Question 8

Which property of water is most directly responsible for the movement of water from roots to leaves in plants?

Accepted Answer

Cohesion and adhesion

Question 9

Which of the following statements about acids, bases, and buffers is correct?

Accepted Answer

Buffers minimize changes in pH by absorbing or releasing H+ ions

Question 10

If the [OH-] in a solution is $$10^{-9}$$ \ 	ext{M}$$, what is the [H+] and pH of the solution?

Accepted Answer

$$[H^+] = 10$$^{-5}$$ \ 	ext{M}, \ pH = 5$$

Question 11

Which of the following best describes why changes in pH can disrupt protein function?

Accepted Answer

Changes in pH can alter the shape of proteins by affecting ionic and hydrogen bonds

Question 12

Which of the following is a consequence of water’s high specific heat for living organisms?

Accepted Answer

Organisms can survive rapid temperature changes in their environment

Question 13

A solution with a pH of 2 has how many times more hydrogen ions than a solution with a pH of 5?

Accepted Answer

1000 times more

Question 14

Which of the following best explains why oil does not dissolve in water?

Accepted Answer

Oil molecules are nonpolar and cannot form hydrogen bonds with water

Question 15

Which of the following is an example of adhesion?

Accepted Answer

Water molecules sticking to the walls of plant vessels

Question 16

What is the effect of adding a strong acid to pure water?

Accepted Answer

The [H+] increases and the pH decreases

Question 17

Which of the following best describes a buffer’s function in biological systems?

Accepted Answer

Buffers keep the pH constant by neutralizing both acids and bases

Question 18

Which property of water is most important for maintaining temperature stability in living organisms?

Accepted Answer

High specific heat

Question 19

Which of the following best explains why living cells must maintain a narrow pH range?

Accepted Answer

Small pH changes can disrupt protein structure and function

Question 20

Which of the following is true about hydrophilic molecules?

Accepted Answer

They dissolve in water or interact with water by hydrogen bonding

Chapter 3: Water and Life – Properties and Biological Importance of Water

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