Q: What is the pH of a solution with a hydrogen ion concentration of $$[H^+] = 1 \times 10$$^{-5}$$ M?

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

Question 1

Which property of water is primarily responsible for the upward movement of water in plants, as shown in the image of the tree?

Accepted Answer

Cohesion and adhesion

Question 2

What type of bond is formed between the hydrogen atom of one water molecule and the oxygen atom of another water molecule, as depicted in the first image?

Accepted Answer

Hydrogen bond

Question 3

Why does ice float on liquid water, as illustrated in the third image?

Accepted Answer

Hydrogen bonds in ice are more ordered, making ice less dense than liquid water

Question 4

A solution is made by dissolving 15 g of CaCl$$_2 in 1 L of $$water. What is the molarity (M) of the solution? (Molar mass of CaCl$$_2 = 111 g/$$mol)

Accepted Answer

$$M = \frac{15}{111} = 0.135 M$$

Question 5

Which of the following best explains why water is an excellent solvent for ionic compounds, as shown in the fourth image?

Accepted Answer

Water molecules are polar and form hydration shells around ions

Question 6

What is the pH of a solution with a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-5}$$ M?

Accepted Answer

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

Question 7

Which property of water allows sweating to cool the human body?

Accepted Answer

Evaporative cooling due to high heat of vaporization

Question 8

A buffer system in blood involves carbonic acid ($$H_2CO_3) $$and bicarbonate ($$HCO_3$$^-$$). What happens when a small amount of acid is added to the blood?

Accepted Answer

The buffer system absorbs excess $$H^+$$, minimizing pH change

Question 9

Which of the following statements about hydrophilic and hydrophobic substances is correct?

Accepted Answer

Hydrophilic substances have an affinity for water and dissolve easily

Question 10

If the pH of a solution changes from 6 to 4, what happens to the hydrogen ion concentration?

Accepted Answer

It increases by 100 times

Question 11

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

Accepted Answer

Hydrogen bonds must absorb heat to break, which moderates temperature changes

Question 12

A protein dissolves in water because it has regions that are:

Accepted Answer

Ionic and polar, allowing interaction with water molecules

Question 13

Which of the following equations correctly represents the relationship between hydrogen ion and hydroxide ion concentrations in pure water at 25°C?

Accepted Answer

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

Question 14

Which of the following is a real-world consequence if ice were denser than liquid water?

Accepted Answer

Bodies of water would freeze from the bottom up, threatening aquatic life

Question 15

How many molecules are present in 2 moles of glucose ($$C_6H_{12}O_6$)? (Avogadro’s number = 6.02$$ 	imes $$10^{23})$$

Accepted Answer

$$2 	imes 6.02 	imes 10$$^{23}$$ = 1.204 	imes 10$$^{24}$$ molecules

Question 16

Which of the following best explains why oil does not dissolve in water?

Accepted Answer

Oil molecules are nonpolar and hydrophobic

Question 17

A solution has a pH of 8. Which of the following statements is true?

Accepted Answer

The solution is basic and has a lower $$[H^+]$$ than pure water

Question 18

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

Accepted Answer

Buffers minimize changes in pH by absorbing or releasing $$H^+$$ ions

Question 19

Which of the following is the correct formula for calculating molarity ($$M$$)?

Accepted Answer

$$M = \frac{	ext{moles of solute}}{	ext{liters of solution}}$$

Water and Life: Properties, Structure, and Biological Importance

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