Question 1

Which statement best describes the law of conservation of matter as it applies to biological systems?

Accepted Answer

Matter cannot be created or destroyed, but it can be rearranged during chemical reactions in living organisms.

Question 2

A neutral atom of sodium (Na) has an atomic number of 11 and an atomic mass of 23. How many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 3

Which of the following best explains why water ($$H_2O) $$and hydrogen peroxide ($$H_2O_2) $$have different properties?

Accepted Answer

Their properties depend on the structure and ratio of their atoms.

Question 4

Which element makes up the largest percentage of body mass in humans?

Accepted Answer

Oxygen

Question 5

What is the main difference between covalent and ionic bonds?

Accepted Answer

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

Question 6

Which of the following is a trace element required by humans in minute amounts?

Accepted Answer

Iron

Question 7

If an atom has 6 protons, 6 neutrons, and 6 electrons, what is its atomic number and atomic mass?

Accepted Answer

Atomic number: $$6$$, Atomic mass: $$12$$

Question 8

Which of the following best describes a compound?

Accepted Answer

A substance consisting of two or more different elements combined in a fixed ratio.

Question 9

Why are noble gases like neon (Ne) and argon (Ar) generally nonreactive?

Accepted Answer

They have a full outer electron shell, satisfying the octet rule.

Question 10

Which of the following best explains the formation of a sodium chloride ($$NaCl) $$crystal?

Accepted Answer

Sodium transfers an electron to chlorine, forming oppositely charged ions that attract each other.

Question 11

Which type of bond is responsible for the partial positive and negative charges in a water molecule?

Accepted Answer

Polar covalent bond

Question 12

What is the maximum number of electrons that can occupy the second electron shell of an atom?

Accepted Answer

$$8$$

Question 13

Which of the following best describes the role of valence electrons in chemical bonding?

Accepted Answer

Valence electrons are the outermost electrons and are involved in forming chemical bonds.

Question 14

Which of the following is true about isotopes of an element?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 15

Which of the following best explains why ionic bonds are weaker in water than in dry conditions?

Accepted Answer

Water molecules surround and separate the ions, reducing the electrostatic attraction between them.

Question 16

A molecule of methane ($$CH_4) is $$formed when carbon shares electrons with four hydrogen atoms. How many total covalent bonds are present in methane?

Accepted Answer

$$4$$ covalent bonds

Question 17

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

Hydrogen bonds are attractions between a hydrogen atom and a strongly electronegative atom like oxygen or nitrogen in another molecule.

Question 18

Which of the following best describes an emergent property in chemistry?

Accepted Answer

A property that arises only when elements are combined in a specific way, such as water's ability to dissolve substances.

Question 19

Which equation correctly represents the chemical reaction for the formation of water from hydrogen and oxygen?

Accepted Answer

$$2H_2 + O_2$ \rightarrow 2H_2O$$

Question 20

Which of the following best explains why elements like carbon, hydrogen, oxygen, and nitrogen are so prevalent in living organisms?

Accepted Answer

Their atomic structures allow them to form a wide variety of stable covalent bonds, supporting complex molecules necessary for life.

Biochemistry Foundations for General Biology: Elements, Atoms, and Chemical Bonds

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