Q: If the concentration of $$[H^+] in a $$solution is $$1 \times 10$$^{-8}$$ M, what is the concentration of $$[OH^-]$$ at 25°C, given that $$[H^+][OH^-] = 1 \times $$10^{-14}$$?

$$[OH^-] = 1 \times 10$$^{-6}$$ M

Question 1

Which property of water is primarily responsible for the transport of water from the roots to the leaves in plants against gravity?

Accepted Answer

Its cohesive behavior due to hydrogen bonding

Question 2

Why does ice float on liquid water, and what is the biological significance of this property?

Accepted Answer

Hydrogen bonds in ice are more ordered, making it less dense than liquid water, allowing ice to float and insulate aquatic environments.

Question 3

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

Accepted Answer

$$pH = 5$$

Question 4

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

Accepted Answer

Water molecules are polar and form hydration shells around ions, separating and dissolving them.

Question 5

If the concentration of $$[H^+] in a $$solution is $$1 	imes 10$$^{-8}$$ M, what is the concentration of $$[OH^-]$$ at 25°C, given that $$[H^+][OH^-] = 1 	imes $$10^{-14}$$?

Accepted Answer

$$[OH^-] = 1 	imes 10$$^{-6}$$ M

Question 6

Which of the following scenarios best illustrates the role of buffers in biological systems?

Accepted Answer

A buffer minimizes changes in pH when small amounts of acid or base are added to blood.

Question 7

Ocean acidification is a result of increased atmospheric $$CO_2. $$What is the chemical process that leads to a decrease in carbonate ion concentration in seawater?

Accepted Answer

$$CO_2$$ reacts with water to form carbonic acid, which dissociates and increases $$H^+$$, combining with carbonate ions to form bicarbonate.

Question 8

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

Accepted Answer

Sweat absorbs heat as it evaporates due to water's high heat of vaporization, removing heat from the body.

Question 9

A patient is suffering from acidosis (low blood pH). Which buffer system in the blood helps to minimize the change in pH, and what is the relevant chemical equation?

Accepted Answer

The bicarbonate buffer system: $$H_2CO_3 \rightleftharpoons $$HCO_3$$^- + H^+$$

Question 10

Which of the following statements about hydrophobic substances is correct?

Accepted Answer

Hydrophobic substances are major components of cell membranes because they are nonpolar and do not mix with water.

Question 11

If you add salt to water, what effect does it have on the freezing point of water, and why?

Accepted Answer

It lowers the freezing point because dissolved ions disrupt the formation of the hydrogen-bonded ice lattice.

Question 12

Which of the following best explains why water has a high specific heat?

Accepted Answer

Hydrogen bonds between water molecules require a large amount of energy to break, so water resists temperature changes.

Question 13

A solution has a pH of 3. How many times more acidic is it than a solution with a pH of 6?

Accepted Answer

1000 times more acidic

Question 14

Which of the following is a consequence of ocean acidification for marine organisms?

Accepted Answer

Decreased carbonate ion concentration, making it harder for organisms to form calcium carbonate shells.

Question 15

Which of the following best describes the relationship between acids, bases, and the concentration of $$H^+$$ ions in solution?

Accepted Answer

Acids increase $$[H^+]$$ and bases decrease $$[H^+].$$

Question 16

Which property of water is most important for maintaining stable temperatures in lakes and oceans?

Accepted Answer

Water's high specific heat

Question 17

A protein is able to dissolve in water because it contains regions that are:

Accepted Answer

Polar or ionic

Question 18

Which of the following equations correctly represents the relationship between $$[H^+]$$ and $$[OH^-] in $$pure water at 25°C?

Accepted Answer

$$[H^+][OH^-] = 1 	imes 10$$^{-14}$$

Question 19

Which of the following best explains why the pH of the stomach is maintained at a low value (around 2)?

Accepted Answer

To provide an optimal environment for digestive enzymes and to kill ingested pathogens.

Water and Life: Properties, Importance, and Biological Roles

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