Q: Which of the following equations represents the product of hydrogen ion and hydroxide ion concentrations in pure water at 25°C?

$[\mathrm{H}^+][\mathrm{OH}^-] = 1 \times 10^{-14}$

Question 1

Which property of water is primarily responsible for the ability of ice to float on liquid water, and what is the molecular basis for this phenomenon?

Accepted Answer

Expansion upon freezing; hydrogen bonds stabilize water molecules in a lattice, making ice less dense than liquid water.

Question 2

A plant transports water from its roots to its leaves. Which two properties of water are most directly involved in this process?

Accepted Answer

Cohesion and adhesion

Question 3

Why does sweating help cool the human body during exercise?

Accepted Answer

Evaporative cooling; water molecules with the highest kinetic energy leave as vapor, lowering the temperature of the remaining liquid.

Question 4

Which equation correctly represents the relationship between hydrogen ion concentration and pH in an aqueous solution?

Accepted Answer

$\mathrm{pH} = -\log_{10}[\mathrm{H}^+]$

Question 5

If the concentration of hydrogen ions $[\mathrm{H}^+]$ in a solution is $1 	imes 10^{-5}$ M, what is the pH of the solution?

Accepted Answer

$\mathrm{pH} = 5$

Question 6

Which of the following best explains why water is an effective solvent for ionic compounds like table salt (NaCl)?

Accepted Answer

Water is polar, so its molecules surround and separate the positive and negative ions.

Question 7

A scientist measures the pH of a lake and finds it to be 4. What is the concentration of hydrogen ions $[\mathrm{H}^+]$ in the lake?

Accepted Answer

$1 	imes 10^{-4}$ M

Question 8

Which emergent property of water helps coastal cities maintain more moderate temperatures compared to inland cities?

Accepted Answer

Ability to moderate temperature due to water's high specific heat

Question 9

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

Accepted Answer

Hydrogen bond

Question 10

Which of the following scenarios best illustrates the cohesive behavior of water?

Accepted Answer

A drop of water maintains its shape on a leaf due to molecules sticking together.

Question 11

During a drought, some plants wilt and die. Which property of water is most directly related to their inability to transport water from roots to leaves?

Accepted Answer

Loss of cohesion and adhesion disrupts water transport in xylem.

Question 12

Which of the following best describes the effect of climate change on Arctic sea ice and its impact on organisms such as ringed seals?

Accepted Answer

Melting sea ice reduces habitat for ringed seals, affecting their ability to hunt and survive.

Question 13

Which of the following equations represents the product of hydrogen ion and hydroxide ion concentrations in pure water at 25°C?

Accepted Answer

$[\mathrm{H}^+][\mathrm{OH}^-] = 1 	imes 10^{-14}$

Question 14

A water-soluble protein is placed in water. What property of water allows the protein to dissolve?

Accepted Answer

Versatility as a solvent due to water's polarity

Question 15

Which of the following is a direct consequence of water's ability to form hydrogen bonds?

Accepted Answer

Water has a high surface tension.

Question 16

If a solution has a pH of 9, which of the following statements is true?

Accepted Answer

The solution is basic, with a low concentration of $[\mathrm{H}^+]$ ions.

Question 17

Which property of water is most important for maintaining stable temperatures in living organisms and environments?

Accepted Answer

High specific heat

Question 18

A student adds hydrochloric acid (HCl) to water, causing the pH to drop from 7 to 2. By what factor did the hydrogen ion concentration increase?

Accepted Answer

100,000 times

Question 19

Which of the following best explains why ice insulates the water below in lakes during winter?

Accepted Answer

Ice floats because it is less dense than liquid water, forming a layer that reduces heat loss from the water below.

Chapter 3: Water and Life – Properties and Biological Importance of Water

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