Question 1

Which of the following best explains why table salt (NaCl) exhibits emergent properties that are different from its constituent elements?

Accepted Answer

Sodium and chlorine form an ionic bond, creating a compound with properties distinct from both elements.

Question 2

A radioactive isotope of nitrogen has 7 protons and 9 neutrons. What are its atomic number and mass number?

Accepted Answer

Atomic number: 7, Mass number: 16

Question 3

Which statement correctly describes the difference between covalent and ionic bonds?

Accepted Answer

Covalent bonds involve sharing electrons, while ionic bonds involve the transfer of electrons.

Question 4

How many covalent bonds can a carbon atom typically form, and why?

Accepted Answer

Four, because carbon has four electrons in its outer shell and needs four more to fill it.

Question 5

Why are the bonds in a water molecule considered polar covalent?

Accepted Answer

Oxygen is more electronegative than hydrogen, so electrons are pulled closer to oxygen.

Question 6

What enables neighboring water molecules to form hydrogen bonds with each other?

Accepted Answer

The polarity of water molecules, with partial positive charges on hydrogen and partial negative charges on oxygen.

Question 7

Which of the following best describes what holds together the ions in a crystal of table salt (NaCl)?

Accepted Answer

Electrostatic attraction between oppositely charged ions.

Question 8

After a hard workout, beads of sweat form on your face. Which property of water is primarily responsible for this phenomenon?

Accepted Answer

Cohesion, because water molecules stick together, forming droplets.

Question 9

Why does ice float on liquid water?

Accepted Answer

Hydrogen bonds in ice cause molecules to be less densely packed than in liquid water.

Question 10

Which equation correctly represents the relationship between hydrogen ion and hydroxide ion concentrations in any aqueous solution at 25°C?

Accepted Answer

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

Question 11

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

Accepted Answer

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

Question 12

Compared to a basic solution at pH 9, the same volume of an acidic solution at pH 4 has how many times more hydrogen ions?

Accepted Answer

100,000 times more

Question 13

Which of the following best explains why blood is classified as an aqueous solution?

Accepted Answer

Blood is a uniform mixture with water as the solvent.

Question 14

Which property of water allows it to moderate temperature in living organisms?

Accepted Answer

Its ability to form hydrogen bonds, which absorb and release heat slowly.

Question 15

A buffer system in blood helps maintain pH homeostasis. Which of the following best describes how a buffer works?

Accepted Answer

It minimizes changes in pH by reversibly binding H+ ions.

Question 16

Which of the following is a real-life consequence of water’s expansion upon freezing?

Accepted Answer

Freezing water expands, which can crack boulders and rocks.

Question 17

Which of the following best describes the role of polarity in water’s ability to dissolve many substances?

Accepted Answer

Water’s polar molecules surround and interact with charged or polar solutes, dissolving them.

Question 18

Which of the following best explains why the internal pH of most living cells must remain close to pH 7?

Accepted Answer

Enzyme activity and cellular processes are highly sensitive to changes in pH.

Question 19

Which of the following is true regarding chemical reactions in living organisms?

Accepted Answer

Chemical reactions rearrange atoms by breaking and forming chemical bonds.

The Chemical Basis of Life: Elements, Atoms, and Water Chemistry

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