Question 1

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

Accepted Answer

NaCl is a compound, and compounds have characteristics different from those of 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 a 100 g sample would remain after 11,460 years?

Accepted Answer

25 g

Question 3

Which of the following best describes a trace element?

Accepted Answer

An element required by an organism in only minute quantities.

Question 4

Which subatomic particle is responsible for the chemical behavior of an atom?

Accepted Answer

Electron

Question 5

A patient is given a radioactive tracer to diagnose thyroid function. Which property of radioactive isotopes makes this possible?

Accepted Answer

They decay spontaneously, emitting particles and energy that can be detected.

Question 6

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

Accepted Answer

They have a full valence shell of electrons.

Question 7

Which of the following is true regarding covalent bonds?

Accepted Answer

A covalent bond involves the sharing of a pair of valence electrons between two atoms.

Question 8

What is the main reason water (H$$_2O) is a $$polar molecule?

Accepted Answer

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

Question 9

Which of the following best describes an ionic bond?

Accepted Answer

An attraction between oppositely charged ions after the transfer of electrons.

Question 10

A molecule of ammonia (NH$$_3) $$can form hydrogen bonds with water molecules. Which atoms are involved in these hydrogen bonds?

Accepted Answer

Hydrogen of ammonia and oxygen of water

Question 11

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

Accepted Answer

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

Question 12

Which of the following is a correct statement about chemical reactions?

Accepted Answer

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

Question 13

If an atom has an atomic number of 7 and a mass number of 15, how many neutrons does it have?

Accepted Answer

8

Question 14

Which of the following best describes van der Waals interactions?

Accepted Answer

Weak attractions between molecules due to temporary local partial charges.

Question 15

Which of the following is the best example of potential energy in a biological system?

Accepted Answer

An electron in a higher energy shell around the nucleus.

Question 16

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 17

A scientist is studying a molecule with the formula C$$_6H$_{12}O$_6. $$Which of the following statements is true about this molecule?

Accepted Answer

It is a compound because it contains more than one element in a fixed ratio.

Question 18

Which of the following best explains why weak chemical bonds are important in biological systems?

Accepted Answer

They allow large biological molecules to maintain their functional forms and enable reversible interactions.

Question 19

Which of the following equations correctly represents the formation of water from its elements?

Accepted Answer

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

Question 20

Which of the following best 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.

The Chemical Context of Life: Foundations for General Biology

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