Question 1

Which of the following statements best explains why sodium chloride (NaCl) has properties different from those of its constituent elements, sodium (Na) and chlorine (Cl)?

Accepted Answer

The emergent properties of NaCl result from the fixed ratio and chemical bonding between sodium and chlorine atoms.

Question 2

A patient is injected with a radioactive isotope to trace metabolic activity in the body. Which property of radioactive isotopes makes this possible?

Accepted Answer

They decay spontaneously, emitting detectable particles and energy.

Question 3

Which of the following best describes the difference between an atom and a molecule?

Accepted Answer

A molecule consists of two or more atoms held together by chemical bonds.

Question 4

Given an atom with atomic number $$Z = 8$$ and mass number $$A = 18$$, how many neutrons does it have?

Accepted Answer

$$10$$

Question 5

Which of the following elements makes up the largest percentage of human body mass?

Accepted Answer

Oxygen

Question 6

A neutral atom of magnesium ($$Mg) $$has an atomic number of $$12$$ and a mass number of $$24. $$Which of the following is true for this atom?

Accepted Answer

It has $$12$$ protons, $$12$$ neutrons, and $$12$$ electrons.

Question 7

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of a pair of valence electrons between atoms.

Question 8

Why are weak chemical interactions, such as hydrogen bonds and van der Waals interactions, important in biological systems?

Accepted Answer

They help maintain the three-dimensional structure and function of large biological molecules.

Question 9

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions are reversible, and equilibrium is reached when the forward and reverse reactions occur at the same rate.

Question 10

A scientist is using radiometric dating to determine the age of a fossil. If the half-life of the parent isotope is $$5,000$$ years and the ratio of parent to daughter isotope is $$1:3$$, how old is the fossil?

Accepted Answer

$$10,000$$ years

Question 11

Which of the following best explains why noble gases are chemically inert?

Accepted Answer

Their valence shells are full, making them stable and unreactive.

Question 12

Which of the following is an example of an ionic bond?

Accepted Answer

The bond between sodium and chlorine in $$NaCl$$

Question 13

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

Accepted Answer

Valence electrons are involved in forming chemical bonds between atoms.

Question 14

A molecule of water ($$H_2O) is $$held together by which type of bond, and what property does this bond confer to water molecules?

Accepted Answer

Polar covalent bond; gives water molecules partial positive and negative charges

Question 15

Which of the following scenarios best illustrates the concept of emergent properties?

Accepted Answer

A single sodium atom is highly reactive, but when combined with chlorine to form sodium chloride, the resulting compound is stable and edible.

Question 16

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 17

Which of the following is a trace element in the human body, making up less than $$0.01\% of $$body mass?

Accepted Answer

Iron

Question 18

If an atom has $$7$$ electrons, $$7$$ protons, and $$8$$ neutrons, what is its atomic number and mass number?

Accepted Answer

Atomic number $$7$$, mass number $$15$$

Question 19

Which of the following best explains why molecular shape is important in biology?

Accepted Answer

Molecular shape determines how molecules recognize and respond to each other.

Question 20

Which of the following statements about van der Waals interactions is correct?

Accepted Answer

They are weak attractions that occur when electrons are distributed asymmetrically in molecules.

The Chemical Context of Life: Foundations for General Biology

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