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 that differ from their constituent elements.

Question 2

Which four elements make up approximately 96% of living matter?

Accepted Answer

Carbon, hydrogen, oxygen, and nitrogen

Question 3

A radioactive isotope of carbon, $$^{14}C$$, is used in medical imaging. What property makes it useful as a tracer in metabolic studies?

Accepted Answer

It emits detectable particles and energy as it decays, allowing tracking in the body.

Question 4

Which statement about electron shells and energy levels is correct?

Accepted Answer

Electrons can move to a higher shell by absorbing energy.

Question 5

An atom has an atomic number of 9 and a mass number of 19. How many neutrons does it have?

Accepted Answer

$$19 - 9 = 10$$ neutrons

Question 6

Which of the following best describes a polar covalent bond?

Accepted Answer

One atom is more electronegative, causing unequal sharing of electrons.

Question 7

What is the main reason noble gases, such as helium and neon, are chemically inert?

Accepted Answer

Their valence shells are full, so they do not tend to form bonds.

Question 8

Which of the following is an example of a weak chemical interaction that is crucial for the three-dimensional structure of large biological molecules?

Accepted Answer

Hydrogen bonds

Question 9

A PET scan uses radioactive tracers to monitor cancer growth. Which property of radioactive isotopes allows this technique to work?

Accepted Answer

They emit energy that can be detected by imaging equipment.

Question 10

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

Accepted Answer

The forward and reverse reactions occur at the same rate.

Question 11

Which statement about ionic bonds is correct?

Accepted Answer

Ionic bonds form when one atom donates an electron to another, resulting in oppositely charged ions that attract each other.

Question 12

Which of the following best explains why water (H$$_2O) is a $$polar molecule?

Accepted Answer

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

Question 13

Which of the following is a real-world example of van der Waals interactions?

Accepted Answer

The ability of a gecko to climb smooth walls due to interactions between its toe hairs and the wall surface

Question 14

A scientist finds a fossil and measures the ratio of a radioactive isotope to its daughter isotope. If the half-life of the isotope is 5,000 years and the ratio indicates three half-lives have passed, how old is the fossil?

Accepted Answer

$$5,000 	imes 3 = 15,000$$ years

Question 15

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

Accepted Answer

A molecule consists of two or more atoms held together by covalent bonds, while a compound consists of two or more different elements in a fixed ratio.

Question 16

Which of the following best explains why trace elements are important for living organisms?

Accepted Answer

They are required in minute quantities but are essential for proper physiological function.

Question 17

Which of the following is the correct balanced chemical equation for photosynthesis?

Accepted Answer

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

Question 18

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions involve the making and breaking of chemical bonds.

Question 19

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

Accepted Answer

Valence electrons are in the outermost shell and determine the chemical behavior of an atom.

Question 20

Which of the following is true about the structure of an atom?

Accepted Answer

Protons and neutrons are found in the nucleus, while electrons form a cloud around the nucleus.

Chapter 2: The Chemical Context of Life – Study Notes

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