Question 1

Which property of water allows insects such as water striders to walk on its surface, and what is the molecular basis for this property?

Accepted Answer

Surface tension resulting from hydrogen bonding between water molecules

Question 2

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

Accepted Answer

$$pH = 4$$

Question 3

Why does ice float on liquid water, and what is the biological significance of this phenomenon?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds keep water molecules farther apart in solid form, insulating aquatic environments

Question 4

Which of the following best explains why water has a high specific heat compared to other substances?

Accepted Answer

Hydrogen bonds between water molecules require significant energy to break and form

Question 5

A scientist adds hydrochloric acid ($$HCl) to $$pure water. What happens to the concentrations of $$[H^+]$$ and $$[OH^-]$$, and how does this affect the pH?

Accepted Answer

$$[H^+]$$ increases, $$[OH^-]$$ decreases, pH decreases

Question 6

Which of the following equations correctly represents the dissociation of water?

Accepted Answer

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

Question 7

A buffer system in blood helps maintain pH near 7.4. If a small amount of acid is added, which reaction will occur to minimize the change in pH?

Accepted Answer

$$HCO_3^- + H$$^+ \rightarrow H_2CO_3$$

Question 8

Which statement best describes the difference between hydrophilic and hydrophobic substances?

Accepted Answer

Hydrophilic substances have an affinity for water due to their polar or ionic nature; hydrophobic substances lack this affinity due to their nonpolar structure

Question 9

If the pH of a solution changes from 6 to 4, how does the hydrogen ion concentration change?

Accepted Answer

It increases by 100 times

Question 10

Which of the following best explains why water is an excellent solvent for ionic compounds?

Accepted Answer

Water molecules surround ions with hydration shells due to their polarity

Question 11

A researcher wants to prepare 1 liter of a 1 M sucrose solution. The molecular weight of sucrose ($$C_{12}H$$_{22}$$O_{11}$) is 342 g/mol. How many grams of sucrose are needed?

Accepted Answer

342 grams

Question 12

Which of the following is a consequence of water's ability to moderate temperature on Earth?

Accepted Answer

Stable climates that support diverse life forms

Question 13

Which of the following is true about acids and bases in aqueous solutions?

Accepted Answer

Acids increase $$[H^+]$$ and decrease pH; bases decrease $$[H^+]$$ and increase pH

Question 14

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

Accepted Answer

Buffers minimize changes in $$[H^+]$$ and $$[OH^-]$$ concentrations, stabilizing pH

Question 15

Which of the following is NOT an emergent property of water that facilitates life?

Accepted Answer

Low specific heat

Question 16

A student mixes sugar into water and observes that it dissolves but does not conduct electricity. What type of substance is sugar in this context?

Accepted Answer

Nonelectrolyte

Question 17

Which of the following best explains the difference between a heterogeneous and a homogeneous mixture?

Accepted Answer

A homogeneous mixture is uniform throughout; a heterogeneous mixture is not

Question 18

If a solution has $$[OH^-] = 1 	imes 10$$^{-8}$$ 	ext{ M}$$, what is its pOH and pH?

Accepted Answer

$$pOH = 8$$, $$pH = 6$$

Question 19

Which of the following reactions represents the formation of a salt from an acid and a base?

Accepted Answer

$$HCl + NaOH \rightarrow NaCl + H_2O$$

Question 20

Ocean acidification is a result of increased atmospheric $$CO_2. $$What is the chemical process that leads to decreased availability of carbonate ions for marine organisms?

Accepted Answer

$$CO_2$$ reacts with $$H_2O to $$form $$H_2CO_3$$, which releases $$H^+$$ and combines with $$CO_3$$^{2-}$$ to form $$HCO_3$$^-$$

Chapter 3: Water and Life – Properties, Chemistry, and Biological Importance

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