Question 1

Which subatomic particle is responsible for the chemical identity of an element, and how is this reflected in the periodic table?

Accepted Answer

Proton; the number of protons (atomic number) defines the element and its position in the periodic table.

Question 2

A radioactive isotope of carbon, $$^{14}C$$, is used in medical imaging. How does $$^{14}C$$ differ from the most common carbon isotope, $$^{12}C$$?

Accepted Answer

$$^{14}C$$ has more neutrons than $$^{12}C$$, making it unstable and radioactive.

Question 3

Which of the following best explains why noble gases like helium and argon are chemically inert?

Accepted Answer

Their outermost electron shell is completely full, making them stable.

Question 4

What type of chemical bond is formed when sodium ($$Na) $$reacts with chlorine ($$Cl) to $$produce table salt ($$NaCl$$)?

Accepted Answer

Ionic bond

Question 5

Which statement correctly describes the difference between polar and nonpolar covalent bonds?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, resulting in molecules with partial charges.

Question 6

Water is considered a polar molecule. Which property of water molecules allows them to form hydrogen bonds?

Accepted Answer

Water molecules have a partial positive charge on hydrogen and a partial negative charge on oxygen.

Question 7

Which property of water allows trees to transport water from their roots to their leaves against gravity?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 8

Why does ice float on liquid water, and what is the biological significance of this property?

Accepted Answer

Ice is less dense than liquid water due to hydrogen bonds spreading water molecules apart, forming an insulating layer that protects aquatic life.

Question 9

A solution has a pH of 4. Which of the following statements is true about this solution?

Accepted Answer

It is acidic, with a higher concentration of $$H^+$$ ions than $$OH^-$$ ions.

Question 10

Which of the following molecules would NOT dissolve in water, and why?

Accepted Answer

Oil, because it is nonpolar and hydrophobic.

Question 11

Which equation correctly represents the dissociation of water molecules?

Accepted Answer

$$H_2O \rightarrow H^+ + OH^-$$

Question 12

A buffer in human blood helps maintain pH by which mechanism?

Accepted Answer

Accepting or releasing $$H^+$$ ions in response to changes in $$H^+$$ concentration.

Question 13

Which of the following best describes a free radical?

Accepted Answer

An atom or molecule with unpaired electrons in its outer shell, making it highly reactive.

Question 14

Which of the following is a real-life example of the importance of water's high heat of vaporization?

Accepted Answer

Sweating cools the human body as water evaporates, absorbing excess heat.

Question 15

Which of the following statements about atomic mass is correct?

Accepted Answer

Atomic mass is the sum of protons and neutrons; electrons have negligible mass.

Question 16

Which of the following best explains why water is an excellent solvent for ionic compounds?

Accepted Answer

Water molecules have partial charges that attract and separate ions.

Question 17

Which of the following is true about the electron shells in atoms?

Accepted Answer

Electrons fill the lowest-energy shell first, and more distant shells hold more electrons.

Question 18

Which of the following is a correct statement about acids and bases in water?

Accepted Answer

Acids release $$H^+$$ ions, while bases increase $$OH^-$$ concentration.

Question 19

Which of the following is a function of antioxidants in the human body?

Accepted Answer

They prevent free radicals from attacking other atoms or molecules by neutralizing them.

Atoms, Molecules, and Water: Foundations of Life

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