Question 1

Which of the following statements best explains why water is considered an excellent solvent for biological reactions?

Accepted Answer

Water's bent geometry and polar nature allow it to form hydrogen bonds with charged and polar molecules, facilitating their dissolution.

Question 2

A radioactive isotope of carbon, carbon-14, has 6 protons and 8 neutrons. What is its mass number?

Accepted Answer

$$14$$

Question 3

Which property of water is most directly responsible for the ability of some insects to walk on its surface?

Accepted Answer

Surface tension due to hydrogen bonding between water molecules

Question 4

If a solution has a hydronium ion concentration $$[H^+] = 1 	imes 10$$^{-4}$$ \ \mathrm{M}$$, what is its pH?

Accepted Answer

$$4$$

Question 5

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

Accepted Answer

Covalent bonds involve sharing electrons between atoms, while ionic bonds involve the transfer of electrons from one atom to another.

Question 6

Which element is most likely to form four covalent bonds in biological molecules due to its number of unpaired electrons?

Accepted Answer

Carbon

Question 7

Why does ice float on liquid water?

Accepted Answer

Ice forms a relatively open crystal structure due to hydrogen bonding, making it less dense than liquid water.

Question 8

A solution has a pH of 2. Which of the following statements is true?

Accepted Answer

The solution is acidic and has a high concentration of $$H^+$$ ions.

Question 9

Which of the following molecules would be least likely to dissolve in water?

Accepted Answer

A nonpolar molecule

Question 10

Which statement best explains why water has a high specific heat?

Accepted Answer

Many hydrogen bonds must be broken for water molecules to move faster, requiring more energy.

Question 11

Which of the following is true about isotopes?

Accepted Answer

Isotopes of an element have different numbers of neutrons, resulting in different masses.

Question 12

Which property of water is most important for the movement of water from plant roots to leaves against gravity?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 13

What is the main reason that polar molecules are hydrophilic?

Accepted Answer

Their partial charges allow them to form hydrogen bonds and electrostatic interactions with water.

Question 14

Which of the following best describes the electron-sharing continuum in chemical bonds?

Accepted Answer

Electrons can be shared equally (nonpolar covalent), unequally (polar covalent), or transferred (ionic) depending on the atoms involved.

Question 15

Which of the following is a consequence of water's ability to form hydrogen bonds?

Accepted Answer

Water has a high capacity for absorbing heat, leading to temperature stability in organisms.

Question 16

A scientist adds a substance to water and observes that the pH decreases. What type of substance was most likely added?

Accepted Answer

An acid, which donates protons

Question 17

Which of the following best explains why living cells maintain a pH close to 7?

Accepted Answer

Enzymes and cellular processes function optimally at neutral pH, and buffers help maintain homeostasis.

Question 18

Which of the following is true about the atomic structure of carbon?

Accepted Answer

Carbon has 6 protons and usually 6 neutrons, allowing it to form four covalent bonds due to four unpaired electrons.

Question 19

Which of the following equations correctly represents the dissociation of water into ions?

Accepted Answer

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

Question 20

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in pH, helping maintain stable conditions for life.

Water and Carbon: The Chemical Basis of Life (Chapter 2 Study Notes)

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