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

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

Q: If the $$[OH^-] in a $$solution is $$1 \times 10$$^{-9}$$ \ \mathrm{M} at$$ $$25^\circ \mathrm{C}$$, what is the pH of the solution?

pH = 5$$\quad ($$since $$[H^+] = 1 \times 10$$^{-5}$$ \ \mathrm{M}$$, $$pH = -\log(1 \times 10$$^{-5}$$) = 5)$$

Question 1

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

Accepted Answer

Cohesion and adhesion

Question 2

A scientist adds a small amount of hydrochloric acid (HCl) to pure water. What happens to the concentration of hydrogen ions $$[H^+]$$ and the pH of the solution?

Accepted Answer

$$[H^+]$$ increases and pH decreases

Question 3

Why does ice float on liquid water, and why is this important for aquatic life in cold climates?

Accepted Answer

Ice is less dense than liquid water due to stable hydrogen bonds, allowing it to float and insulate the water below

Question 4

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

Accepted Answer

Hydrogen bonds between water molecules absorb heat when they break and release heat when they form

Question 5

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 6

Which of the following best describes a hydrophobic substance?

Accepted Answer

It repels water because it contains relatively nonpolar bonds

Question 7

If the $$[OH^-] in a $$solution is $$1 	imes 10$$^{-9}$$ \ \mathrm{M} at$$ $$25^\circ \mathrm{C}$$, what is the pH of the solution?

Accepted Answer

pH = 5$$\quad ($$since $$[H^+] = 1 	imes 10$$^{-5}$$ \ \mathrm{M}$$, $$pH = -\log(1 	imes 10$$^{-5}$$) = 5)$$

Question 8

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

Accepted Answer

A buffer minimizes changes in pH when acids or bases are added to a solution

Question 9

Which property of water allows it to dissolve a wide variety of substances, making it the 'universal solvent'?

Accepted Answer

Its polarity, which allows it to form hydrogen bonds with many solutes

Question 10

A lake receives acid precipitation with a pH of 4.6. How many times more acidic is this precipitation compared to neutral water (pH 7)?

Accepted Answer

About 2500 times more acidic $$\quad ($$since $$10^{7-4.6}$$ \approx 2512$$)

Question 11

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

Accepted Answer

Sweat absorbs heat as it evaporates, due to water's high heat of vaporization

Question 12

Which of the following statements about acids and bases is correct?

Accepted Answer

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

Question 13

A solution has a pH of 8. What is the $$[OH^-]$$ concentration?

Accepted Answer

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

Question 14

Which of the following is an example of adhesion?

Accepted Answer

Water molecules forming hydrogen bonds with plant cell walls

Question 15

If a solution has $$[H^+] = 1 	imes 10$$^{-9}$$ \ \mathrm{M}$$, what is its pH and is it acidic, basic, or neutral?

Accepted Answer

pH = 9; basic

Question 16

Which of the following best describes the relationship between $$[H^+]$$ and $$[OH^-] in $$pure water at $$25^\circ \mathrm{C}$$?

Accepted Answer

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

Question 17

A buffer is added to a solution. Which of the following best describes its effect?

Accepted Answer

It minimizes changes in pH by accepting or donating $$H^+$$ ions

Question 18

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

Accepted Answer

Decreased ability of corals to form calcium carbonate reefs

Question 19

Which of the following best explains why water is essential for most biochemical reactions in living organisms?

Accepted Answer

Water's polarity allows it to dissolve many solutes, facilitating molecular collisions

Water: The Molecule That Supports Life – Properties and Importance in Biology

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