Question 1

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

Accepted Answer

Because the oxygen atom is more electronegative than the hydrogen atoms, creating partial charges.

Question 2

Which property of water allows it to moderate temperature changes in coastal regions?

Accepted Answer

High heat of vaporization and specific heat

Question 3

A solution has a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-4}$$ M. What is its pH?

Accepted Answer

$$pH = 4$$

Question 4

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice form a stable, open lattice that makes ice less dense than liquid water.

Question 5

Which of the following molecules would be most likely to dissolve in water?

Accepted Answer

A molecule with polar covalent bonds

Question 6

What type of bond is formed between the oxygen atom of one water molecule and the hydrogen atom of another water molecule?

Accepted Answer

Hydrogen bond

Question 7

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

Accepted Answer

Buffers resist changes in pH by accepting or donating hydrogen ions.

Question 8

A solution with a pH of 3 has how many times more hydrogen ions than a solution with a pH of 6?

Accepted Answer

1000 times more

Question 9

Which of the following statements about hydrogen bonds is TRUE?

Accepted Answer

Hydrogen bonds are weak individually but strong in large numbers.

Question 10

Which of the following best explains why salt (NaCl) dissolves in water?

Accepted Answer

The partial negative charge on oxygen in water is attracted to Na$$^+$$, and the partial positive charge on hydrogen is attracted to Cl$$^-.$$

Question 11

Which of the following is a consequence of water’s cohesion?

Accepted Answer

Surface tension that allows insects to walk on water

Question 12

Which of the following best describes why carbon dioxide (CO$$_2) is a $$nonpolar molecule, even though it contains polar covalent bonds?

Accepted Answer

CO$$_2 is $$linear and symmetrical, so the dipoles cancel out.

Question 13

Which of the following is NOT an emergent property of water due to hydrogen bonding?

Accepted Answer

Water’s ability to dissolve nonpolar molecules

Question 14

Which of the following best describes the relationship between pH and hydrogen ion concentration?

Accepted Answer

As pH decreases, $$[H^+]$$ increases.

Question 15

Which of the following is TRUE about the bond between the oxygen and hydrogen within a water molecule?

Accepted Answer

It is a polar covalent bond.

Question 16

Which of the following best explains why nonpolar molecules are hydrophobic?

Accepted Answer

They cannot form hydrogen bonds with water.

Question 17

Which of the following is a real-life example of water’s high heat of vaporization?

Accepted Answer

Sweating cools the human body as water evaporates from the skin.

Question 18

Which of the following best describes the role of hydrogen bonds in DNA?

Accepted Answer

They hold the two strands of the double helix together.

Question 19

A solution has a pH of 5. What is the hydrogen ion concentration?

Accepted Answer

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

Water and Its Essential Role in Life: Structure, Properties, and Biological Significance

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