$$pH = -\log(1 \times 10$$^{-5}$$) = 5$$

Question 1

Which property of water allows a spider 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 why is this important for aquatic life in cold climates?

Accepted Answer

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

Question 3

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

Accepted Answer

$$pH = -\log(1 	imes 10$$^{-5}$$) = 5$$

Question 4

Which of the following best explains why coastal cities tend to have milder climates than inland cities at the same latitude?

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 statements about acids and bases is correct?

Accepted Answer

An acid increases the concentration of H$$^+ in a $$solution.

Question 6

How many grams of NaOH (molecular mass = 40 g/mol) are needed to make 1 liter of a 1 M NaOH solution?

Accepted Answer

40 g

Question 7

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

Accepted Answer

Buffers minimize changes in pH by reversibly binding H$$^+$$ ions.

Question 8

If the pH of a solution changes from 6 to 4, how does the concentration of H$$^+$$ ions change?

Accepted Answer

It increases by 100 times.

Question 9

Which of the following molecules would be most likely to dissolve in water?

Accepted Answer

A polar molecule like glucose

Question 10

What is the main reason water is an effective solvent for ionic compounds like NaCl?

Accepted Answer

Water molecules are polar and form hydration shells around ions.

Question 11

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

Accepted Answer

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

Question 12

A patient’s blood pH drops from 7.4 to 7.1. What physiological response would you expect from the bicarbonate buffer system?

Accepted Answer

Bicarbonate ions ($$\mathrm{$$HCO_3$$^-}) $$will combine with H$$^+ to $$form carbonic acid ($$\mathrm{H_2CO_3}).$$

Question 13

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

Accepted Answer

Evaporation of sweat absorbs heat from the body due to water’s high heat of vaporization.

Question 14

Which of the following is true about hydrophobic substances?

Accepted Answer

They are typically nonpolar and do not dissolve in water.

Question 15

What is the molarity (M) of a solution containing 18 grams of glucose (molecular mass = 180 g/mol) dissolved in 0.5 liters of water?

Accepted Answer

0.1 M

Question 16

Which property of water is most directly responsible for the movement of water from roots to leaves in plants?

Accepted Answer

Cohesion and adhesion

Question 17

If a solution has a pH of 9, what is the concentration of H$$^+$$ ions?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-9}$$ M

Question 18

Which of the following best describes why oil and water do not mix?

Accepted Answer

Oil molecules are nonpolar and hydrophobic, so they do not interact with polar water molecules.

Question 19

Which of the following is a real-life consequence of the loss of Arctic sea ice due to global warming?

Accepted Answer

Decreased survival of species that depend on ice, such as polar bears and walruses.

Water and Life: Properties, Acids, Bases, and pH

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