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

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

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 without sinking?

Accepted Answer

Cohesion due to hydrogen bonding

Question 2

Why does ice float on liquid water, and what would be the ecological consequence if it did not?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds keep molecules farther apart; if ice sank, bodies of water would freeze solid, threatening aquatic life.

Question 3

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}$$ \ \mathrm{M}$$

Question 4

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

Accepted Answer

Water has a high specific heat, allowing it to absorb and release large amounts of heat with little temperature change.

Question 5

Which of the following scenarios demonstrates the concept of evaporative cooling?

Accepted Answer

A dog pants to cool itself after running.

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 why oil does not dissolve in water?

Accepted Answer

Oil molecules are nonpolar and cannot form hydrogen bonds with water.

Question 8

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

Accepted Answer

pH = 4

Question 9

Which of the following is a real-world consequence of ocean acidification caused by increased atmospheric $$CO_2$$?

Accepted Answer

Decreased availability of carbonate ions for marine organisms

Question 10

A buffer solution contains a weak acid and its conjugate base. What happens when a small amount of strong acid is added to this buffer?

Accepted Answer

The buffer neutralizes the added acid, minimizing the change in pH.

Question 11

Which property of water is most important for the movement of water from the roots to the leaves in tall trees?

Accepted Answer

Cohesion and adhesion

Question 12

Which of the following best describes the relationship between temperature and kinetic energy in water molecules?

Accepted Answer

Temperature is the average kinetic energy of the molecules.

Question 13

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

Accepted Answer

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

Question 14

A solution has a pH of 9. Which of the following statements is true?

Accepted Answer

The solution is basic and has more $$[OH^-]$$ than $$[H^+].$$

Question 15

Which of the following best explains why water is an effective solvent for ionic and polar substances?

Accepted Answer

Water is polar and forms hydration shells around ions and polar molecules.

Question 16

If a lake receives a large input of acid rain, which property of the lake water would help minimize a drastic change in pH?

Accepted Answer

Presence of buffers

Question 17

Which of the following is a direct effect of hydrogen bonding in water?

Accepted Answer

Water has a high specific heat and high surface tension.

Question 18

A researcher wants to prepare 0.5 L of a 2 M glucose solution ($$C_6H_{12}O_6$, molecular mass = 180 g/mol). How many grams of glucose should she use?

Accepted Answer

180 g

Question 19

Which of the following best describes the role of carbonate ions ($$CO_3$$^{2-}$$) in marine ecosystems?

Accepted Answer

They are required for the formation of calcium carbonate shells by marine organisms.

Water and Life: Properties, Structure, and Biological Importance

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