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

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

Question 1

Which property of water allows it to moderate Earth's climate by absorbing and releasing large amounts of heat with only slight changes in its own temperature?

Accepted Answer

High specific heat

Question 2

A scientist adds a small amount of hydrochloric acid ($\mathrm{HCl}$) to pure water. Which of the following best describes what happens to the pH and why?

Accepted Answer

The pH decreases because $\mathrm{HCl}$ donates hydrogen ions ($\mathrm{H^+}$)

Question 3

Which of the following best explains why ice floats on liquid water?

Accepted Answer

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

Question 4

A solution has a pH of 4. What is the concentration of hydrogen ions ($[\mathrm{H^+}]$) in this solution?

Accepted Answer

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

Question 5

Which of the following best describes a hydrophobic substance?

Accepted Answer

It repels water and does not form hydrogen bonds with water

Question 6

A beaker contains a solution with a pH of 9. Which of the following statements is true about this solution?

Accepted Answer

It is basic and has a low concentration of $\mathrm{H^+}$ ions

Question 7

Which of the following scenarios best illustrates the adhesive property of water?

Accepted Answer

Water climbing up a paper towel dipped into a glass of water

Question 8

If a solution has a pH of 6 and another has a pH of 8, how many times greater is the hydrogen ion concentration in the first solution compared to the second?

Accepted Answer

100 times greater

Question 9

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers maintain a stable pH by accepting or donating $\mathrm{H^+}$ ions

Question 10

A protein is denatured in a solution with a very low pH. Which property of water is most directly involved in this process?

Accepted Answer

Water's ability to act as a solvent for ionic and polar substances

Question 11

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

Accepted Answer

$\mathrm{H_2O} \rightarrow \mathrm{H^+} + \mathrm{OH^-}$

Question 12

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

Accepted Answer

Evaporation of sweat absorbs heat due to water's high heat of vaporization

Question 13

A solution contains $[\mathrm{H^+}] = 1 	imes 10^{-7}\ \mathrm{M}$. What is the pH of this solution?

Accepted Answer

pH = 7

Question 14

Which of the following is an example of water's cohesive behavior?

Accepted Answer

Water molecules forming droplets due to hydrogen bonding

Question 15

A patient is given an intravenous solution that is hypertonic compared to their blood plasma. What is the most likely effect on their red blood cells?

Accepted Answer

The cells will shrink as water leaves the cells

Question 16

Which of the following best describes the difference between hydrophilic and hydrophobic substances?

Accepted Answer

Hydrophilic substances dissolve in water, while hydrophobic substances do not

Question 17

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

Accepted Answer

Cohesion and adhesion

Question 18

A solution is made by dissolving $0.01$ moles of sodium hydroxide ($\mathrm{NaOH}$) in $1$ liter of water. What is the pOH of the solution? (Assume complete dissociation.)

Accepted Answer

pOH = 2

Question 19

Which of the following best explains why salt (NaCl) dissolves easily in water?

Accepted Answer

The polar water molecules surround and separate the Na$^+$ and Cl$^-$ ions

Question 20

A biologist observes that a certain protein is only soluble in water at a specific pH. Which property of water is most relevant to this observation?

Accepted Answer

Water's ability to act as a solvent for charged and polar molecules

Water and Life: Study Notes for General Biology

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