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

Question 1

Which of the following best explains why water molecules are more cohesive than molecules of most other substances?

Accepted Answer

Water molecules form extensive hydrogen bonds with each other.

Question 2

In a solution of salt water, which component is the solvent and which is the solute?

Accepted Answer

Water is the solvent; salt is the solute.

Question 3

Why is ice less dense than liquid water, allowing it to float?

Accepted Answer

Hydrogen bonds in ice force water molecules into a lattice that spaces them farther apart.

Question 4

Which property of water is most directly responsible for the ability of some insects to walk on water?

Accepted Answer

Cohesion due to hydrogen bonding

Question 5

A scientist adds a drop of oil to a beaker of water. The oil does not dissolve. Which term best describes the oil?

Accepted Answer

Hydrophobic

Question 6

Which of the following best explains why water acts as a temperature stabilizer in living organisms?

Accepted Answer

Water has a high specific heat due to hydrogen bonding, so it resists temperature changes.

Question 7

Which equation correctly relates pH to the concentration of hydrogen ions $$[H^+] in $$solution?

Accepted Answer

$$\mathrm{pH} = -\log_{10} [H^+]$$

Question 8

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 9

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

Accepted Answer

It increases by 100 times.

Question 10

Which of the following best describes the role of a buffer in a biological system?

Accepted Answer

A buffer minimizes changes in pH by accepting or donating H$$^+$$ ions.

Question 11

Which of the following is an example of adhesion in biological systems?

Accepted Answer

Water molecules forming hydrogen bonds with the cellulose in plant cell walls

Question 12

A patient’s blood pH drops from 7.4 to 7.1. Which of the following best describes this change?

Accepted Answer

The blood has become more acidic.

Question 13

Which of the following substances would most likely be soluble in water?

Accepted Answer

A polar molecule such as glucose

Question 14

Why is a high heat of vaporization important for living organisms?

Accepted Answer

It enables evaporative cooling, helping organisms regulate temperature.

Question 15

Which of the following best distinguishes an acid from a base?

Accepted Answer

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

Question 16

A solution has a pH of 9. Which of the following best describes this solution?

Accepted Answer

It is basic and has a low concentration of H$$^+$$ ions.

Question 17

Which of the following best explains why changes in pH can be dangerous for living organisms?

Accepted Answer

pH changes can disrupt enzyme activity and cellular processes.

Question 18

A student mixes 0.1 mol of hydrochloric acid (HCl) in 1 L of water. What is the resulting pH of the solution? (Assume complete dissociation.)

Accepted Answer

pH = 1

Question 19

Which of the following best describes the relationship between molarity and pH in an acidic solution?

Accepted Answer

As molarity of H$$^+$$ increases, pH decreases.

Question 20

A biologist is studying the movement of water up a plant stem. Which two properties of water are most directly responsible for this process?

Accepted Answer

Cohesion and adhesion

Study Guide: Water and pH (General Biology - Chapter 2.5)

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