Q: Which of the following is a correct calculation for the hydrogen ion concentration of a solution with pH 12?

$$[H^+] = 1 \times 10$$^{-12}$$\ \mathrm{M}$$

Question 1

Which property of water allows it to move upward through the stem of a plant against gravity, as seen in capillary action?

Accepted Answer

Its cohesive and adhesive interactions

Question 2

Why does ice float on liquid water, and what is the biological significance of this phenomenon?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds keep water molecules further apart in the solid state, preventing bodies of water from freezing solid and insulating aquatic ecosystems.

Question 3

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

Accepted Answer

$$pH = 7$$

Question 4

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, removing energy from the skin.

Question 5

Which of the following scenarios demonstrates water’s property as a versatile solvent?

Accepted Answer

Salt (NaCl) dissolves readily in water due to the attraction between water’s partial charges and the ions.

Question 6

A buffer solution contains a weak acid and its conjugate base. What happens when a small amount of strong acid is added to this buffer?

Accepted Answer

The buffer absorbs the excess $$H^+$$ ions, minimizing the change in pH.

Question 7

Which of the following best describes the difference between heat and temperature?

Accepted Answer

Heat is the total kinetic energy of molecules, while temperature is the average kinetic energy of molecules.

Question 8

If the hydroxide ion concentration in a solution is $$[OH^-] = 1 	imes 10$$^{-8}$$\ \mathrm{M}$$, what is the pH of the solution at 25°C?

Accepted Answer

$$pH = 6$$

Question 9

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

Accepted Answer

A large amount of energy is required to break hydrogen bonds between water molecules.

Question 10

A scientist adds hydrochloric acid (HCl) to pure water. What happens to the $$[H^+]$$ and $$[OH^-]$$ concentrations?

Accepted Answer

$$[H^+]$$ increases and $$[OH^-]$$ decreases

Question 11

Which of the following best describes why water beads up on a plastic spoon but soaks into a paper towel?

Accepted Answer

Plastic is hydrophobic and nonpolar, so water does not adhere, while paper is hydrophilic and polar, allowing adhesion and capillary action.

Question 12

Which of the following is a correct calculation for the hydrogen ion concentration of a solution with pH 12?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-12}$$\ \mathrm{M}$$

Question 13

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

Accepted Answer

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

Question 14

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

Accepted Answer

Acids increase $$[H^+] in $$solution, bases decrease $$[H^+]$$, and buffers minimize changes in pH.

Question 15

Which of the following best describes the molecular structure of water and its consequences?

Accepted Answer

Water is a polar molecule with polar covalent bonds, leading to hydrogen bonding between molecules.

Question 16

A solution has $$[H^+] = 1 	imes 10$$^{-5}$$\ \mathrm{M}. $$What is the $$[OH^-]$$ concentration at 25°C?

Accepted Answer

$$[OH^-] = 1 	imes 10$$^{-9}$$\ \mathrm{M}$$

Question 17

Which of the following is an example of water’s cohesion?

Accepted Answer

Water droplets forming beads on a waxed car surface due to hydrogen bonding between water molecules.

Question 18

Which of the following best describes why small changes in pH can have large biological effects?

Accepted Answer

pH is a logarithmic scale, so each unit change represents a tenfold change in $$[H^+]$$ concentration.

Question 19

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

Accepted Answer

Oil is hydrophobic and consists of nonpolar covalent bonds, so it does not interact favorably with polar water molecules.

Water: Structure, Properties, and Biological Significance

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