Q: A solution has a hydrogen ion concentration of $$1 \times 10$$^{-5}$$ M. What is its pH?

$$pH = -\log [1 \times 10$$^{-5}$$] = 5$$

Question 1

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Hydrogen bonds in ice are more 'ordered,' making ice less dense than liquid water.

Question 2

Which property of water allows coastal cities to have milder climates compared to inland cities?

Accepted Answer

Water's high specific heat

Question 3

A solution has a hydrogen ion concentration of $$1 	imes 10$$^{-5}$$ M. What is its pH?

Accepted Answer

$$pH = -\log [1 	imes 10$$^{-5}$$] = 5$$

Question 4

Which of the following is NOT one of the four emergent properties of water that contribute to Earth's suitability for life?

Accepted Answer

High viscosity

Question 5

Why can water dissolve many ionic and polar substances?

Accepted Answer

Water forms hydration shells around solutes due to its polarity.

Question 6

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

Accepted Answer

Buffers minimize changes in concentrations of $$H^+$$ and $$OH^-$$ ions.

Question 7

A plant is able to transport water from its roots to its leaves against gravity. Which property of water is most responsible for this phenomenon?

Accepted Answer

Cohesion and adhesion

Question 8

If the pH of a solution changes from 6 to 4, what happens to the hydrogen ion concentration?

Accepted Answer

It increases by 100-fold.

Question 9

Which of the following explains why sweating cools the body?

Accepted Answer

Evaporative cooling removes heat as water molecules with the highest kinetic energy leave as gas.

Question 10

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

Accepted Answer

An acid increases the $$H^+$$ concentration of a solution.

Question 11

Why is water considered a polar molecule?

Accepted Answer

It has an uneven distribution of charge due to polar covalent bonds.

Question 12

Which of the following is a consequence if ice were denser than liquid water?

Accepted Answer

Bodies of water would freeze from the bottom up, threatening aquatic life.

Question 13

What is the molarity of a solution containing 0.5 moles of NaCl dissolved in 1 liter of water?

Accepted Answer

$$0.5\ M$$

Question 14

Which of the following best describes a hydrophobic substance?

Accepted Answer

It does not mix with water due to nonpolar covalent bonds.

Question 15

Which equation correctly represents the dissociation of water?

Accepted Answer

$$2H_2O \rightleftharpoons H_3O^+ + OH^-$$

Question 16

Which of the following is true about the carbonic acid-bicarbonate buffer system in blood?

Accepted Answer

It maintains blood pH by both donating and absorbing $$H^+$$ ions.

Question 17

Which property of water is most important for the survival of aquatic organisms during winter?

Accepted Answer

Expansion upon freezing

Question 18

A solution is prepared by dissolving 18 g of glucose ($$C_6H_{12}O_6$, molar mass = 180 g/mol) in enough water to make 0.5 L of solution. What is the molarity of the solution?

Accepted Answer

$$0.2\ M$$

Question 19

Which of the following best explains why oil does not mix with water?

Accepted Answer

Oil molecules have relatively more nonpolar covalent bonds.

Question 20

What is the product of $$[H^+][OH^-] in $$any aqueous solution at 25°C?

Accepted Answer

$$10^{-14}$$

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

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