$$\text{Mass number} = \text{Atomic number} + \text{Number of neutrons}$$

Question 1

Which of the following statements best explains why water is considered a universal solvent in biological systems?

Accepted Answer

Water is polar, allowing it to dissolve many ionic and polar substances by surrounding and separating their ions or molecules.

Question 2

A neutral atom of carbon has an atomic number of 6 and a mass number of 12. How many neutrons does it have?

Accepted Answer

$$6$$

Question 3

Which property of water is most directly responsible for the ability of some insects to walk on water?

Accepted Answer

Surface tension

Question 4

If a solution has a pH of 4, which of the following statements is true?

Accepted Answer

The solution is acidic and has a high concentration of H$$^+$$ ions.

Question 5

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electrons between two atoms.

Question 6

A radioactive isotope of an element differs from a stable isotope in that it:

Accepted Answer

Emits radiation due to an unstable nucleus.

Question 7

Which of the following equations correctly represents the relationship between atomic number, mass number, and neutrons?

Accepted Answer

$$	ext{Mass number} = 	ext{Atomic number} + 	ext{Number of neutrons}$$

Question 8

Why does ice float on liquid water?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds create an open lattice structure.

Question 9

Which of the following is a consequence of water’s high specific heat for living organisms?

Accepted Answer

Water helps stabilize internal and external temperatures, protecting organisms from drastic fluctuations.

Question 10

A buffer system in blood helps maintain pH homeostasis by:

Accepted Answer

Absorbing or releasing H$$^+ or OH$^-$$ ions to keep pH within a narrow range.

Question 11

Which of the following best describes the difference between polar and nonpolar covalent bonds?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons; nonpolar covalent bonds involve equal sharing.

Question 12

Which property of water is most important for the process of sweating and cooling the human body?

Accepted Answer

High heat of vaporization

Question 13

Which of the following is true about hydrogen bonds?

Accepted Answer

They are weak attractions between polar molecules, such as between water molecules.

Question 14

Which of the following best explains why oxygen, carbon, and hydrogen make up the majority of body mass?

Accepted Answer

They are the most abundant elements in biological molecules and are involved in key chemical reactions necessary for life.

Question 15

A molecule of NaCl (table salt) is best described as:

Accepted Answer

A compound formed by ionic bonds between sodium and chlorine.

Question 16

Which of the following is the correct definition of an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 17

Which of the following best describes the role of electronegativity in chemical bonding?

Accepted Answer

Electronegativity is the ability of an atom to attract electrons in a bond, influencing whether a bond is polar or nonpolar.

Question 18

Which of the following best explains why water is able to dissolve salts such as NaCl?

Accepted Answer

Water is polar and can stabilize the separated Na$$^+$$ and Cl$$^-$$ ions by surrounding them with its partial charges.

Question 19

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

Accepted Answer

Acids release H$$^+$$ ions and bases accept H$$^+$$ ions.

Question 20

A scientist discovers a new atom with 8 protons, 10 neutrons, and 8 electrons. What is its atomic number and mass number?

Accepted Answer

Atomic number: $$8$$, Mass number: $$18$$

Chapter 2: The Chemistry of Life – Study Guide

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