Question 1

Which property of water is primarily responsible for the ability of some insects, such as water striders, to walk on the surface of a pond?

Accepted Answer

High surface tension due to cohesive hydrogen bonding

Question 2

A lake does not freeze solid in winter, even when air temperatures are below freezing for months. Which property of water best explains this phenomenon?

Accepted Answer

Water's expansion upon freezing, making ice less dense than liquid water

Question 3

Which of the following best describes the difference between covalent and hydrogen bonds in water?

Accepted Answer

Covalent bonds hold the atoms within a water molecule together, while hydrogen bonds form between different water molecules

Question 4

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

Accepted Answer

$$5$$

Question 5

Why is water considered a 'universal solvent' in biological systems?

Accepted Answer

Its polarity allows it to dissolve many ionic and polar substances

Question 6

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

Accepted Answer

Evaporation of sweat absorbs heat due to water's high heat of vaporization

Question 7

A buffer solution is added to a beaker of pure water. Which of the following best describes the buffer's function if a strong acid is then added?

Accepted Answer

The buffer will accept hydrogen ions to minimize the change in pH

Question 8

If the pH of human blood drops from 7.4 to 7.0, what happens to the hydrogen ion concentration?

Accepted Answer

It increases by a factor of $$2.5^{10}$$ \approx 25

Question 9

Which of the following scenarios best illustrates the importance of water's high specific heat for living organisms?

Accepted Answer

A pond remains at a relatively stable temperature throughout the day, despite large fluctuations in air temperature

Question 10

A scientist adds a strong base, NaOH, to a solution. Which of the following chemical equations best represents the dissociation of NaOH in water?

Accepted Answer

$$\mathrm{NaOH} \rightarrow \mathrm{Na}^+ + \mathrm{OH}^-$$

Question 11

Which of the following best explains why water expands upon freezing?

Accepted Answer

Hydrogen bonds become more rigid and form a crystalline lattice, increasing the space between molecules

Question 12

A solution has a pH of 3. What is the hydrogen ion concentration $$[H^+] in $$this solution?

Accepted Answer

$$1 	imes 10$$^{-3}$$ M

Question 13

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

Accepted Answer

Ice would sink, causing lakes to freeze from the bottom up and threatening aquatic life

Question 14

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

Accepted Answer

Buffers minimize changes in pH by accepting or donating hydrogen ions

Question 15

A student adds hydrochloric acid (HCl) to pure water. Which of the following best describes what happens to the pH and why?

Accepted Answer

The pH decreases because HCl donates hydrogen ions, increasing $$[H^+]$$

Question 16

Which of the following best explains why water is able to climb up the stem of a plant during transpiration?

Accepted Answer

Water's cohesive and adhesive properties allow it to move against gravity through capillary action

Question 17

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

Accepted Answer

Acids donate $$H^+$$ ions to solution, while bases accept $$H^+$$ ions or donate $$OH^-$$ ions

Question 18

A buffer system in blood involves carbonic acid ($$H_2CO_3) $$and bicarbonate ($$HCO_3$$^-$$). Which equation best represents the buffer's response to a drop in pH?

Accepted Answer

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

Question 19

Which of the following best explains why polar molecules are hydrophilic?

Accepted Answer

They form hydrogen bonds with water due to their partial charges

Question 20

If a solution has a pH of 8, how does its hydrogen ion concentration compare to a solution with a pH of 6?

Accepted Answer

It is 100 times lower

Properties of Water, pH, and Biological Buffers – General Biology Study Notes

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