Question 1

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Hydrogen bonds in ice cause water molecules to be spaced farther apart than in liquid water.

Question 2

A patient is injected with a radioactive isotope for a PET scan. Which property of isotopes allows this technique to work?

Accepted Answer

Living cells cannot distinguish between isotopes of the same element, so radioactive tracers are incorporated into normal metabolic processes.

Question 3

Which of the following elements makes up the largest percentage of the human body by weight?

Accepted Answer

Oxygen

Question 4

What type of chemical bond is formed when two atoms share electrons equally?

Accepted Answer

Nonpolar covalent bond

Question 5

Which of the following best describes a buffer in a biological system?

Accepted Answer

A buffer minimizes changes in pH by accepting or donating H$$^+$$ ions as needed.

Question 6

A solution has a pH of 4. What is the concentration of H$$^+$$ ions compared to a solution with a pH of 6?

Accepted Answer

100 times higher

Question 7

Which of the following is a trace element essential for the prevention of goiter in humans?

Accepted Answer

Iodine

Question 8

What is the main reason water is an excellent solvent for ionic and polar substances?

Accepted Answer

Water molecules are polar, allowing them to surround and interact with charged and polar solutes.

Question 9

Which of the following equations correctly represents the chemical reaction for the formation of water from hydrogen and oxygen?

Accepted Answer

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

Question 10

Which property of water allows plants to transport water from roots to leaves?

Accepted Answer

Cohesion due to hydrogen bonding

Question 11

A sodium atom transfers an electron to a chlorine atom. What type of bond is formed between the resulting ions?

Accepted Answer

Ionic bond

Question 12

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions rearrange matter by making and breaking chemical bonds.

Question 13

Which of the following best describes the difference between an atom and an ion?

Accepted Answer

An ion has gained or lost electrons and thus has a charge, while an atom is electrically neutral.

Question 14

Which of the following is a real-world consequence of acid precipitation?

Accepted Answer

Damage to forests and aquatic ecosystems due to lower pH in rain, snow, or fog

Question 15

Which of the following best explains why water has a high specific heat compared to other substances?

Accepted Answer

Hydrogen bonds between water molecules absorb heat when they break and release heat when they form.

Question 16

A solution with a pH of 2 has how many times more H$$^+$$ ions than a solution with a pH of 5?

Accepted Answer

1,000 times more

Question 17

Which of the following is true about isotopes of the same element?

Accepted Answer

They have the same number of protons but different numbers of neutrons.

Question 18

Which property of water is most important for maintaining a stable temperature in living organisms?

Accepted Answer

Water's ability to moderate temperature due to hydrogen bonding

Question 19

Which of the following best describes the role of electronegativity in the formation of polar covalent bonds?

Accepted Answer

A difference in electronegativity between atoms causes unequal sharing of electrons, resulting in partial charges.

Question 20

Which of the following is an example of a compound?

Accepted Answer

Sodium chloride (NaCl)

The Chemical Basis of Life: Elements, Atoms, Compounds, and Water

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