Question 1

Which property of water is primarily responsible for the ability of some insects to walk on water surfaces?

Accepted Answer

Cohesion resulting in high surface tension

Question 2

A scientist adds 58 g of NaCl (molecular mass = 58 g/mol) to enough water to make 1 liter of solution. What is the molarity of the solution?

Accepted Answer

$$1\ \mathrm{M}$$

Question 3

Why does ice float on liquid water?

Accepted Answer

Ice is less dense than liquid water because its molecules are locked into a crystalline lattice by hydrogen bonds.

Question 4

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

Accepted Answer

Water molecules are polar and can form hydration shells around ions and polar molecules.

Question 5

A solution has a hydrogen ion concentration of $$[H^+] = 1 	imes 10$$^{-5}$$\ \mathrm{M}. $$What is the pH of this solution?

Accepted Answer

$$5$$

Question 6

Which of the following is a real-world consequence of ocean acidification?

Accepted Answer

Decreased carbonate ion availability, making it harder for marine organisms to build shells

Question 7

If you mix 0.1 mol of acetic acid (a weak acid) and 0.1 mol of sodium acetate (its conjugate base) in 1 L of water, what is the primary function of this solution?

Accepted Answer

To act as a buffer and resist changes in pH

Question 8

Which of the following best describes a hydrophobic substance?

Accepted Answer

It is nonpolar and does not interact favorably with water.

Question 9

A student prepares a solution by dissolving 42.23 g of $$NH_4Cl ($$molar mass = 53.50 g/mol) in enough water to make 500.0 mL of solution. What is the molarity of the solution?

Accepted Answer

$$1.58\ \mathrm{M}$$

Question 10

Which of the following statements about water's high specific heat is correct?

Accepted Answer

It helps moderate temperature fluctuations in the environment.

Question 11

A solution is made by mixing 3.60 x $$10^{-3}$$ mol of NaOH and 5.95 x $$10^{-4}$$ mol of HCl in enough water to make 1.00 L. What is the pH of the resulting solution? (Assume complete neutralization and that NaOH and HCl are strong base and acid, respectively.)

Accepted Answer

$$pH = 12.77$$

Question 12

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 13

Which of the following is true about the relationship between pH and $$[H^+] in an $$aqueous solution?

Accepted Answer

As $$[H^+]$$ increases, pH decreases.

Question 14

Which of the following is a direct result of water’s ability to form hydrogen bonds?

Accepted Answer

Water has a high surface tension.

Question 15

A solution has a pH of 3. What is the hydrogen ion concentration $$[H^+]$$?

Accepted Answer

$$1 	imes 10$$^{-3}$$\ \mathrm{M}$$

Question 16

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

Accepted Answer

Buffers minimize changes in pH by accepting or donating H+ ions.

Question 17

Which of the following would NOT dissolve well in water?

Accepted Answer

Olive oil

Question 18

If the pH of a solution changes from 7 to 5, what happens to the hydrogen ion concentration?

Accepted Answer

It increases by 100-fold.

Question 19

Which of the following is a consequence if all ice sank instead of floated?

Accepted Answer

Lakes and oceans would freeze from the bottom up, threatening aquatic life.

Question 20

Which of the following best explains why coastal areas tend to have milder climates than inland areas?

Accepted Answer

Water’s high specific heat allows it to absorb and release large amounts of heat with little temperature change.

Water and Life: Properties, Chemistry, and Biological Importance

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