Question 1

Which of the following best explains why water (H$$_2O) is a $$polar molecule?

Accepted Answer

Because the oxygen atom is more electronegative than the hydrogen atoms, creating an unequal sharing of electrons and a bent molecular shape.

Question 2

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

Accepted Answer

$$4$$

Question 3

Which of the following statements about hydrogen bonds is CORRECT?

Accepted Answer

Hydrogen bonds form between a partially positive hydrogen atom and a partially negative atom such as oxygen or nitrogen.

Question 4

Why does ice float on liquid water?

Accepted Answer

Because hydrogen bonds in ice are more stable and hold water molecules further apart, making ice less dense than liquid water.

Question 5

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

Accepted Answer

A nonpolar molecule such as methane (CH$$_4)$$

Question 6

A solution with a pH of 5 has how many times more hydrogen ions than a solution with a pH of 7?

Accepted Answer

$$100$$ times more

Question 7

Which property of water allows it to moderate temperature changes in the environment?

Accepted Answer

High specific heat due to hydrogen bonding

Question 8

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 9

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 10

If the electronegativity difference between two atoms is $$1.8$$, what type of bond is most likely to form?

Accepted Answer

Ionic bond

Question 11

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

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 12

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

Accepted Answer

Water molecules form hydration shells around Na$$^+$$ and Cl$$^-$$ ions, separating them from the crystal.

Question 13

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 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 NOT an emergent property of water due to hydrogen bonding?

Accepted Answer

Water has a low specific heat.

Question 16

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

Accepted Answer

They cannot form hydrogen bonds with water.

Question 17

A patient’s blood pH drops from 7.4 to 7.1. By what factor has the hydrogen ion concentration increased?

Accepted Answer

About 2 times (actually 10$$^{0.3}$$ ≈ 2), but the correct answer is 2 times.

Question 18

Which of the following is a real-life example of hydrogen bonding in biological systems?

Accepted Answer

The double helix structure of DNA is stabilized by hydrogen bonds between base pairs.

Question 19

Which of the following best describes the effect of adding a strong acid to pure water?

Accepted Answer

The $$[H^+]$$ increases and the pH decreases.

Water: Structure, Polarity, and Its Essential Role in Biology

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