Question 1

Which of the following best explains why sodium chloride (NaCl) has properties different from both sodium metal and chlorine gas?

Accepted Answer

NaCl is a compound, and compounds have emergent properties different from their constituent elements.

Question 2

A radioactive isotope of carbon, $$^{14}C$$, is used in radiometric dating. If the half-life of $$^{14}C is 5$$,730 years, how much of an original 100 g sample would remain after 11,460 years?

Accepted Answer

$$25\ \mathrm{g}$$

Question 3

Which statement correctly describes the relationship between atomic number and atomic mass?

Accepted Answer

Atomic number is the number of protons; atomic mass is the sum of protons and neutrons.

Question 4

Which of the following best describes why water ($$\mathrm{H_2O}) is a $$polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons.

Question 5

A PET scan uses radioactive isotopes to detect cancerous tissue. Which property of radioactive isotopes makes this possible?

Accepted Answer

They emit energy and particles as they decay, which can be detected by imaging equipment.

Question 6

Which of the following is true about valence electrons and chemical reactivity?

Accepted Answer

Atoms with incomplete valence shells tend to form chemical bonds to achieve stability.

Question 7

Which of the following best describes a hydrogen bond?

Accepted Answer

A bond formed when a hydrogen atom covalently bonded to one electronegative atom is attracted to another electronegative atom.

Question 8

Which of the following is an example of a chemical reaction?

Accepted Answer

$$2\ \mathrm{H_2$} + \mathrm{O_2$} \rightarrow 2\ \mathrm{H_2O}$$

Question 9

Why are van der Waals interactions important in biological systems, such as a gecko climbing a wall?

Accepted Answer

They allow for temporary attractions between molecules, which can collectively be strong enough to support the gecko's weight.

Question 10

Which of the following best explains why morphine and endorphins can both bind to the same receptors in the brain?

Accepted Answer

They have similar molecular shapes, allowing them to fit into the same receptor sites.

Question 11

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 12

Which equation correctly represents the process of photosynthesis?

Accepted Answer

$$6\ \mathrm{CO_2$} + 6\ \mathrm{H_2O} \rightarrow \mathrm{C_6H_{12}O_6$} + 6\ \mathrm{O_2$}$$

Question 13

Which of the following best describes chemical equilibrium in a reversible reaction?

Accepted Answer

The forward and reverse reactions occur at the same rate, and the concentrations of reactants and products remain constant.

Question 14

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

Accepted Answer

Iron (Fe)

Question 15

Which of the following statements about covalent bonds is correct?

Accepted Answer

A single covalent bond involves the sharing of one pair of electrons.

Question 16

Which of the following best describes an ionic bond?

Accepted Answer

An attraction between oppositely charged ions formed by the transfer of electrons.

Question 17

Which of the following is NOT a property of matter?

Accepted Answer

Ability to be broken down into other substances by chemical reactions.

Question 18

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

Accepted Answer

They have full valence electron shells.

Question 19

Which of the following is the best definition of Avogadro’s number?

Accepted Answer

The number of particles in one mole of a substance.

Chapter 2: The Chemical Context of Life – Study Notes

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