Question 1

Which property of water is primarily responsible for its ability to moderate Earth's temperature and thus support life?

Accepted Answer

Its high specific heat due to hydrogen bonding

Question 2

A sodium chloride (NaCl) crystal is placed in water. What happens at the molecular level to allow NaCl to dissolve?

Accepted Answer

Water molecules form hydration shells around Na+ and Cl- ions, separating them from the crystal lattice

Question 3

Which of the following best explains why water is an effective solvent for polar substances?

Accepted Answer

Water's polarity allows it to form hydrogen bonds with other polar molecules

Question 4

Which emergent property of water is most directly responsible for the formation of ice on the surface of lakes, allowing aquatic life to survive beneath during winter?

Accepted Answer

Expansion upon freezing

Question 5

A solution is made by dissolving glucose (a polar molecule) in water. Which of the following best describes the interaction between glucose and water molecules?

Accepted Answer

Hydrogen bonds form between the hydroxyl groups of glucose and water molecules

Question 6

Which of the following statements about hydrogen bonds in water is correct?

Accepted Answer

Hydrogen bonds form between the partially positive hydrogen of one water molecule and the partially negative oxygen of another

Question 7

If a solution has a pH of 4, what is the concentration of hydrogen ions $$[H^+] in $$the solution?

Accepted Answer

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

Question 8

A solution has a pH of 9. What is its pOH, and is the solution acidic, neutral, or basic?

Accepted Answer

pOH = 5; the solution is basic

Question 9

Which of the following best describes a hydrophobic substance?

Accepted Answer

A nonpolar molecule that does not dissolve in water

Question 10

If the pH of a solution changes from 6 to 4, how does the hydrogen ion concentration change?

Accepted Answer

It increases by 100 times

Question 11

Which of the following is NOT an emergent property of water that contributes to Earth's suitability for life?

Accepted Answer

Low viscosity

Question 12

A student adds a nonpolar oil to water and observes that the oil forms droplets rather than dissolving. Which property of water explains this observation?

Accepted Answer

Water is polar and does not interact favorably with nonpolar molecules

Question 13

Which of the following equations correctly relates pH and hydrogen ion concentration?

Accepted Answer

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

Question 14

A solution has $$[OH^-] = 10$$^{-9}$$ \, \mathrm{M}. $$What is the pH of the solution?

Accepted Answer

pH = 5

Question 15

Why does water have a partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms?

Accepted Answer

Oxygen is more electronegative than hydrogen, pulling shared electrons closer

Question 16

Which of the following best explains why salt (NaCl) dissolves in water but oil does not?

Accepted Answer

NaCl is ionic and interacts with water's polarity, while oil is nonpolar and cannot form hydrogen bonds with water

Question 17

A biologist wants to prepare a buffer solution that resists changes in pH. Which property of water is most important for the buffer's function?

Accepted Answer

Water's ability to dissociate into $$H^+$$ and $$OH^-$$ ions

Question 18

Which of the following best describes a hydration shell?

Accepted Answer

A layer of water molecules surrounding a dissolved ion

Question 19

If a solution at 25°C has $$[H^+] = 10$$^{-7}$$ \, \mathrm{M}$$, what is its pH and is it acidic, basic, or neutral?

Accepted Answer

pH = 7; neutral

Question 20

Which of the following real-life scenarios best illustrates the cohesive property of water?

Accepted Answer

Water droplets forming beads on a car windshield

Water and the Chemistry of Life: Properties, Solutions, and Biological Molecules

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