Question 1

Which property of water is primarily responsible for the formation of droplets on a leaf after rainfall?

Accepted Answer

Cohesion due to hydrogen bonding between water molecules

Question 2

Water is described as a polar molecule. What is the main reason for this polarity?

Accepted Answer

The difference in electronegativity between oxygen and hydrogen atoms

Question 3

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

Accepted Answer

Hydrogen bonds in ice create a lattice that is less dense than liquid water

Question 4

A solution is made by dissolving 1 mole of NaCl in 1 liter of water. What is the molarity of NaCl in this solution?

Accepted Answer

$$1.0\ \mathrm{M}$$

Question 5

Which equation correctly represents the dissociation of water molecules?

Accepted Answer

$$2\ \mathrm{H_2O} \rightarrow \mathrm{H_3O^+} + \mathrm{OH^-}$$

Question 6

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

Accepted Answer

$$5$$

Question 7

Which of the following statements about buffers is correct?

Accepted Answer

Buffers minimize changes in pH by accepting or donating $$\mathrm{H^+}$$ ions

Question 8

A patient’s blood pH drops from 7.4 to 7.1. Which buffer system is most likely to respond to restore pH?

Accepted Answer

Carbonic acid-bicarbonate buffer system

Question 9

Which of the following molecules is hydrophobic?

Accepted Answer

Squalene ($$\mathrm{C$$_{30}$$H_{50}})$$

Question 10

Which property of water allows it to dissolve ionic compounds such as NaCl?

Accepted Answer

Water’s polarity and ability to surround charged particles

Question 11

A weak acid, such as carbonic acid ($$\mathrm{H_2CO_3}$$), partially dissociates in water. What is the equilibrium expression for its dissociation?

Accepted Answer

$$K_a = \frac{[\mathrm{H^+}][\mathrm{$$HCO_3$$^-}]}{[\mathrm{H_2CO_3}]}$$

Question 12

Which of the following best describes the relationship between $$[\mathrm{H^+}]$$ and $$[\mathrm{OH^-}] in $$pure water at 25°C?

Accepted Answer

$$[\mathrm{H^+}] = [\mathrm{OH^-}]$$

Question 13

Which of the following is a direct consequence of water’s high specific heat for living organisms?

Accepted Answer

Water resists changes in temperature, helping to stabilize climates and body temperatures

Question 14

A solution has a pH of 3. How many times greater is the $$[\mathrm{H^+}]$$ concentration compared to a solution with pH 6?

Accepted Answer

$$1000$$ times greater

Question 15

Which of the following best explains why water can climb up the stem of a plant against gravity?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 16

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

Accepted Answer

Acids increase $$[\mathrm{H^+}]$$ and bases increase $$[\mathrm{OH^-}]$$

Question 17

Which of the following is a real-world example of water’s surface tension?

Accepted Answer

A water strider insect walking on the surface of a pond

Question 18

Which of the following best describes the role of weak acids and their conjugate bases in biological systems?

Accepted Answer

They act as buffers to maintain stable pH

Question 19

A scientist adds hydrochloric acid ($$\mathrm{HCl}) to $$pure water. What immediate effect does this have on the solution?

Accepted Answer

The $$[\mathrm{H^+}]$$ increases and pH decreases

Water, Acids, Bases, Buffers, and pH in Biological Systems

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