Question 1

Which of the following statements best explains why ice floats on liquid water, and why this property is crucial for aquatic life in cold climates?

Accepted Answer

Ice is less dense than liquid water because water expands as it freezes, allowing ice to float and insulate the water below, protecting aquatic life.

Question 2

A radioactive isotope is used in a PET scan to trace metabolic activity in the brain. Which property of isotopes makes this possible?

Accepted Answer

Isotopes have the same chemical behavior as stable atoms but can emit radiation due to their unstable nuclei.

Question 3

Which of the following best describes the difference between ionic and covalent bonds?

Accepted Answer

Ionic bonds involve the attraction between oppositely charged ions, while covalent bonds involve the sharing of electrons between atoms.

Question 4

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⁺ than OH⁻.

Question 5

Which property of water allows it to move upward through the vessels of a plant against gravity?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 6

Given the balanced equation for photosynthesis: $$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2$$, how many oxygen atoms are present on the reactant side?

Accepted Answer

18

Question 7

Which of the following best explains why water has a high heat of vaporization?

Accepted Answer

The many hydrogen bonds between water molecules require a large amount of energy to break for evaporation.

Question 8

A patient with diabetes is experiencing acidosis. Which of the following best describes what is happening in their body?

Accepted Answer

Their body cannot buffer extra H⁺ ions, causing blood pH to drop below normal limits.

Question 9

Which of the following is a correct statement about the arrangement of electrons in an atom with atomic number 12 (magnesium)?

Accepted Answer

The first shell contains 2 electrons, the second shell contains 8 electrons, and the third shell contains 2 electrons.

Question 10

Which of the following best describes a buffer’s role in biological systems?

Accepted Answer

A buffer maintains pH by taking up excess H⁺ or OH⁻ ions, preventing drastic changes in pH.

Question 11

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

Accepted Answer

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

Question 12

Why is water considered an excellent solvent for ionic compounds like NaCl?

Accepted Answer

Water’s polarity and hydrogen bonding allow it to surround and dissociate ions.

Question 13

Which of the following best explains why the chemical properties of an atom are largely determined by the arrangement of its electrons?

Accepted Answer

The arrangement of electrons, especially in the valence shell, determines how atoms interact and bond with other atoms.

Question 14

Which of the following is a real-world example of the importance of water’s high heat capacity?

Accepted Answer

Water in lakes and oceans helps moderate Earth’s climate by absorbing and releasing heat slowly.

Question 15

A sodium atom (Na) has 11 protons and 11 electrons. After it loses one electron to form Na⁺, what is the resulting charge and why?

Accepted Answer

The charge is +1 because it has one more proton than electrons.

Question 16

Which of the following best describes the octet rule as it applies to atoms with more than two electron shells?

Accepted Answer

Atoms are most stable when their outermost shell contains eight electrons.

Question 17

Which of the following is a correct interpretation of the pH scale?

Accepted Answer

A solution with pH 7 has equal concentrations of H⁺ and OH⁻ ions.

Question 18

Which of the following best explains why water molecules are attracted to each other?

Accepted Answer

Hydrogen bonds form between the slightly positive hydrogen of one water molecule and the slightly negative oxygen of another.

Question 19

Which of the following is an example of a compound, as defined in chemistry?

Accepted Answer

H₂O (water)

Chapter 2: The Chemical Basis of Life – Essentials of Biology Study Notes

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