Question 1

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

Accepted Answer

NaCl is a compound, and compounds have emergent properties that differ from the elements that form them due to the fixed ratio and chemical bonding of their atoms.

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 iodine is commonly used in medical imaging to track thyroid function. What property of radioactive isotopes makes them useful as tracers in biological systems?

Accepted Answer

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

Question 4

Which of the following best describes the difference between a covalent bond and an ionic bond?

Accepted Answer

A covalent bond involves the sharing of electrons, while an ionic bond involves the transfer of electrons from one atom to another.

Question 5

Which of the following statements about valence electrons is correct?

Accepted Answer

The number of valence electrons determines the chemical behavior of an atom.

Question 6

A molecule of water (H$$_2O) is $$held together by which type of bond, and what property of oxygen leads to the polarity of the molecule?

Accepted Answer

Covalent bonds; oxygen is more electronegative than hydrogen, resulting in unequal sharing of electrons.

Question 7

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

Accepted Answer

They have a full valence shell of electrons, making them stable and unlikely to react.

Question 8

Which of the following is an example of a trace element, and why are trace elements important for living organisms?

Accepted Answer

Iodine (I); trace elements are required in minute quantities but are essential for specific biological functions.

Question 9

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

Accepted Answer

$$15 - 7 = 8$$ neutrons

Question 10

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 11

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

Accepted Answer

Sodium is a soft metal and chlorine is a poisonous gas, but together they form edible table salt (NaCl).

Question 12

Which of the following best describes the difference between a polar covalent bond and a nonpolar covalent bond?

Accepted Answer

In a polar covalent bond, electrons are shared unequally due to differences in electronegativity; in a nonpolar covalent bond, electrons are shared equally.

Question 13

Which of the following best explains why water is an effective solvent for ionic compounds like NaCl?

Accepted Answer

Water molecules are polar, allowing them to surround and separate the positive and negative ions in the salt.

Question 14

Which of the following is true about van der Waals interactions?

Accepted Answer

They are weak attractions that occur when electrons are distributed asymmetrically in molecules, allowing close molecules to attract each other.

Question 15

A patient is injected with a radioactive tracer to monitor metabolic activity in the brain. Which property of the tracer allows doctors to visualize its movement?

Accepted Answer

The tracer emits detectable particles and energy as it decays.

Question 16

Which of the following best describes the relationship between atomic number and the identity of an element?

Accepted Answer

The atomic number is the number of protons in the nucleus, which determines the element's identity.

Question 17

Which of the following best explains why chemical reactions are essential for life?

Accepted Answer

Chemical reactions make and break chemical bonds, allowing the transformation of matter necessary for biological processes.

Question 18

Which of the following is the correct balanced chemical equation for the formation of water from hydrogen and oxygen?

Accepted Answer

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

Question 19

A carbon atom has 6 protons, 6 neutrons, and 6 electrons. If it gains a neutron, what is the resulting atom called?

Accepted Answer

An isotope of carbon

Question 20

Which of the following best describes the role of electrons in determining the chemical properties of an atom?

Accepted Answer

The distribution of electrons, especially in the valence shell, determines how an atom interacts and bonds with other atoms.

Chapter 2: The Chemical Context of Life – Study Notes

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