$$1 \times 10$$^{-7}$$\ \mathrm{M}$$

Question 1

Which property of water allows insects like water striders to walk on the surface of a pond without sinking?

Accepted Answer

High surface tension due to cohesion

Question 2

A water molecule is described as polar because:

Accepted Answer

The oxygen atom has a partial negative charge and the hydrogen atoms have partial positive charges

Question 3

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Hydrogen bonds in ice cause water molecules to be spaced farther apart, making ice less dense

Question 4

If a lake has a pH of 4.0, what is the concentration of hydrogen ions in the lake?

Accepted Answer

$$[H^+] = 10$$^{-4}$$\ \mathrm{M}$$

Question 5

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

Accepted Answer

Ability to dissolve nonpolar substances

Question 6

A solution has a pH of 9. What is the concentration of hydroxide ions ($$[OH^-]) in $$this solution?

Accepted Answer

$$[OH^-] = 10$$^{-5}$$\ \mathrm{M}$$

Question 7

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

Accepted Answer

Buffers minimize changes in pH by accepting or donating $$H^+$$ ions

Question 8

A protein requires a specific pH to function properly. What should be added to the solution to maintain this pH?

Accepted Answer

Buffer

Question 9

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

Accepted Answer

Stable internal and external environments

Question 10

What type of bond is responsible for the cohesion of water molecules?

Accepted Answer

Hydrogen bond

Question 11

Which of the following substances would be considered hydrophobic?

Accepted Answer

Oil

Question 12

If the pH of a solution changes from 6 to 4, how does the hydrogen ion concentration change?

Accepted Answer

It increases by 100 times

Question 13

Which of the following best describes the molecular structure of water?

Accepted Answer

Bent (V-shaped), with polar covalent bonds

Question 14

What is the molarity of $$H^+$$ ions in pure water at 25°C?

Accepted Answer

$$1 	imes 10$$^{-7}$$\ \mathrm{M}$$

Question 15

Which of the following is true about acids?

Accepted Answer

They increase the concentration of $$H^+$$ ions in solution

Question 16

Why is water considered a versatile solvent?

Accepted Answer

It forms hydrogen bonds with charged and polar molecules

Question 17

Which of the following would happen if the hydrophobic glycolipid coating on skin were removed?

Accepted Answer

Water would be lost from skin cells more quickly

Question 18

A student mixes salt ($$NaCl) $$into water. What happens at the molecular level?

Accepted Answer

Na$$^+$$ ions interact with the partial negative charge of oxygen atoms in water

Question 19

Which equation correctly represents the relationship between $$[H^+]$$ and $$[OH^-] in $$any aqueous solution at 25°C?

Accepted Answer

$$[H^+][OH^-] = 10$$^{-14}$$

Question 20

Which of the following best describes the function of carbonic acid and bicarbonate in human blood?

Accepted Answer

They act as a buffer system to regulate pH

Chapter 3: Water and Life – Properties, Structure, and Biological Importance

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