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 type of bond is formed by the sharing of electrons equally between two atoms?

Accepted Answer

Nonpolar covalent bond

Question 3

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice are stable and hold water molecules apart, making ice less dense than liquid water.

Question 4

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

Accepted Answer

$$pH = 4$$

Question 5

Which of the following is NOT a property of water that results from hydrogen bonding?

Accepted Answer

Water is a good solvent for nonpolar molecules.

Question 6

Which of the following best describes a hydrogen bond?

Accepted Answer

An attraction between a partially positive hydrogen atom and a partially negative atom like oxygen or nitrogen.

Question 7

If the pH of a solution changes from 7 to 5, how does the hydrogen ion concentration change?

Accepted Answer

It increases by 100 times.

Question 8

Which of the following molecules would be hydrophobic?

Accepted Answer

A nonpolar molecule such as methane ($$CH_4)$$

Question 9

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

Accepted Answer

Acids donate $$H^+$$ ions and decrease pH; bases accept $$H^+$$ ions and increase pH.

Question 10

Why does table salt ($$NaCl) $$dissolve easily in water?

Accepted Answer

The partial charges on water molecules surround and separate the $$Na^+$$ and $$Cl^-$$ ions.

Question 11

Which of the following best explains why coastal cities have milder climates than inland cities?

Accepted Answer

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

Question 12

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

Accepted Answer

It is a polar covalent bond.

Question 13

A molecule has polar covalent bonds but is symmetrical in shape. What is the overall polarity of the molecule?

Accepted Answer

Nonpolar

Question 14

Which of the following best describes the role of hydrogen bonds in biological macromolecules?

Accepted Answer

They help stabilize the structure of proteins and DNA.

Question 15

Which of the following best describes a buffer in a biological system?

Accepted Answer

A chemical that resists changes in pH by accepting or donating $$H^+$$ ions.

Question 16

Which of the following is a consequence of water's high heat of vaporization for living organisms?

Accepted Answer

Evaporative cooling helps regulate body temperature.

Question 17

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

Hydrogen bonds are much weaker than covalent bonds but are crucial for the structure of water and biomolecules.

Question 18

A solution has a pH of 2. What is the hydrogen ion concentration $$[H^+]$$?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-2}$$ \ M$$

Question 19

Which of the following best explains why nonpolar molecules do not dissolve in water?

Accepted Answer

Nonpolar molecules cannot form hydrogen bonds with water.

Question 20

Which of the following is true about the pH scale?

Accepted Answer

Each unit change represents a tenfold change in $$[H^+]$$ concentration.

Water and Its Essential Role in Life: Structure, Bonds, and Properties

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