Q: A solution has a pH of 4. What is the concentration of hydrogen ions $$[H^+] in $$this solution?

$$[H^+] = 1 \times 10$$^{-4}$$ M

Question 1

Which property of water is primarily responsible for the ability of some insects to walk on its surface?

Accepted Answer

Cohesion due to hydrogen bonding

Question 2

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice keep water molecules farther apart, making ice less dense

Question 3

Which of the following best explains why coastal areas tend to have milder climates than inland areas?

Accepted Answer

Water’s high specific heat allows it to absorb and release heat slowly, moderating temperature

Question 4

A solution has a pH of 4. What is the concentration of hydrogen ions $$[H^+] in $$this solution?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-4}$$ M

Question 5

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

Accepted Answer

Water exhibits cohesion and high surface tension

Question 6

A scientist dissolves 58.44 g of NaCl (molecular mass = 58.44 g/mol) in enough water to make 1 L of solution. What is the molarity (M) of the solution?

Accepted Answer

1 M

Question 7

Which of the following best describes a buffer’s function in biological systems?

Accepted Answer

Buffers minimize changes in pH by accepting or donating $$H^+$$ ions

Question 8

What is the main product of fossil fuel combustion that leads to ocean acidification?

Accepted Answer

$$CO_2$$

Question 9

Which of the following statements about hydrophobic substances is correct?

Accepted Answer

They are typically composed of nonpolar bonds

Question 10

If the concentration of $$[OH^-] in a $$solution is $$1 	imes 10$$^{-10}$$ M at 25°C, what is the pH of the solution?

Accepted Answer

pH = 4

Question 11

Which property of water explains why sweating cools the human body?

Accepted Answer

Evaporative cooling due to high heat of vaporization

Question 12

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

Accepted Answer

Water’s polarity allows it to form hydration shells around ions

Question 13

A lake has a pH of 6. After acid rain, the pH drops to 4. How many times greater is the hydrogen ion concentration in the lake after the acid rain?

Accepted Answer

100 times greater

Question 14

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 density as a solid

Question 15

Which equation correctly represents the dissociation of water?

Accepted Answer

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

Question 16

Which of the following scenarios best illustrates the concept of adhesion?

Accepted Answer

Water climbing up the walls of a thin glass tube

Question 17

What is the effect of ocean acidification on marine organisms that build shells from calcium carbonate ($$CaCO_3$$)?

Accepted Answer

It decreases the availability of carbonate ions, making shell building more difficult

Question 18

Which of the following best describes a hydrophilic substance?

Accepted Answer

It has an affinity for water and dissolves easily

Question 19

A buffer solution contains carbonic acid ($$H_2CO_3) $$and bicarbonate ($$HCO_3$$^-$$). What happens when a small amount of acid is added to this solution?

Accepted Answer

$$HCO_3$$^-$$ will combine with H$$^+$$ to form H_2CO_3$

Question 20

Which of the following is true about the relationship between temperature and kinetic energy in water?

Accepted Answer

Temperature measures the average kinetic energy of water molecules

Water and Life: Properties, Structure, and Biological Importance

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