Q: A solution has a hydrogen ion concentration of $$[H^+] = 1 \times 10$$^{-5}$$ M. What is the pH of this solution?

$$pH = -\log(1 \times 10$$^{-5}$$) = 5$$

Q: If the concentration of hydroxide ions in a solution is $$[OH^-] = 1 \times 10$$^{-3}$$ M, what is the pH of the solution at 25°C?

$$pOH = -\log(1 \times 10$$^{-3}$$) = 3$$, so pH = 14 - 3 = 11$

Question 1

Which property of water is primarily responsible for the ability of trees to transport water from their roots to their leaves against gravity?

Accepted Answer

Cohesion and adhesion

Question 2

Why does ice float on liquid water?

Accepted Answer

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

Question 3

A solution has a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-5}$$ M. What is the pH of this solution?

Accepted Answer

$$pH = -\log(1 	imes 10$$^{-5}$$) = 5$$

Question 4

Which of the following best explains why sweating cools the human body?

Accepted Answer

Evaporation of sweat absorbs heat from the body due to water's high heat of vaporization.

Question 5

A buffer solution contains carbonic acid ($$H_2CO_3) $$and bicarbonate ($$HCO_3$$^-$$). What happens if a small amount of acid is added to this solution?

Accepted Answer

$$HCO_3$$^-$$ will combine with the added H$$^+$$ to form H_2CO_3$, minimizing the pH change.

Question 6

Which of the following statements about water’s specific heat is correct?

Accepted Answer

Water’s high specific heat allows it to minimize temperature changes, stabilizing environments for life.

Question 7

Which of the following best describes a hydrophobic substance?

Accepted Answer

A substance that does not have an affinity for water and is typically nonpolar.

Question 8

If the concentration of hydroxide ions in a solution is $$[OH^-] = 1 	imes 10$$^{-3}$$ M, what is the pH of the solution at 25°C?

Accepted Answer

$$pOH = -\log(1 	imes 10$$^{-3}$$) = 3$$, so pH = 14 - 3 = 11$

Question 9

Which property of water explains why salt (NaCl) dissolves easily in water?

Accepted Answer

Water’s polarity allows it to surround and separate ions, forming hydration shells.

Question 10

A scientist prepares a 1 M solution of glucose ($$C_6H_{12}O_6$) by dissolving 180 g in enough water to make 1 L of solution. What does the '1 M' represent?

Accepted Answer

1 mole of glucose per liter of solution

Question 11

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

Accepted Answer

Lakes and oceans cool slowly at night, moderating coastal climates.

Question 12

Which of the following best describes how buffers maintain pH in biological systems?

Accepted Answer

Buffers donate or accept $$H^+$$ ions to minimize changes in pH.

Question 13

A solution has a pH of 4. What is the hydrogen ion concentration?

Accepted Answer

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

Question 14

Which of the following is NOT a consequence of water’s cohesive behavior?

Accepted Answer

Water’s ability to dissolve salts

Question 15

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

Accepted Answer

Oil molecules are nonpolar and hydrophobic, so they do not interact with water’s polar molecules.

Question 16

If a solution has a pH of 9, what is its $$[OH^-]$$ concentration?

Accepted Answer

$$pOH = 14 - 9 = 5$$, so [OH^-] = $$10^{-5}$ M

Question 17

Which of the following is an example of water’s ability to moderate temperature?

Accepted Answer

A lake remains relatively warm in autumn, even as air temperature drops.

Question 18

Which of the following is true about acids and bases?

Accepted Answer

Acids increase $$[H^+]$$ and bases decrease $$[H^+] in a $$solution.

Question 19

Which of the following best describes the relationship between pH and $$[H^+]$$?

Accepted Answer

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

Chapter 3: Water and Life – Properties, Biological Roles, and Chemical Context

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