$$\text{Molecular weight} = \sum \text{atomic weights of all atoms in molecule}$$

$$[H^+] = 1 \times 10$$^{-4}$$ \text{M}$$

Question 1

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

Accepted Answer

Water's bent shape and highly polar covalent bonds allow it to form hydrogen bonds with charged and polar molecules.

Question 2

Which element is NOT one of the four most abundant atoms in living organisms?

Accepted Answer

Phosphorus

Question 3

A radioactive isotope of carbon decays over time. What property distinguishes this isotope from stable carbon?

Accepted Answer

It has a different number of neutrons.

Question 4

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally, spending more time near the more electronegative atom.

Question 5

What is the correct formula for calculating the mass of one mole of a molecule?

Accepted Answer

$$	ext{Molecular weight} = \sum 	ext{atomic weights of all atoms in molecule}$$

Question 6

Which property of water is MOST responsible for its ability to dissolve ionic compounds like NaCl?

Accepted Answer

Its overall polarity and ability to form hydrogen bonds

Question 7

If a solution has a pH of 4, what is the concentration of hydrogen ions ($$[H^+]) in $$moles per liter?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-4}$$ 	ext{M}$$

Question 8

Which functional group acts as a base by attracting protons?

Accepted Answer

Amino group

Question 9

What is the main difference between condensation (dehydration) and hydrolysis reactions in biological systems?

Accepted Answer

Condensation reactions join monomers into polymers, releasing water; hydrolysis breaks polymers into monomers, consuming water.

Question 10

Which statement about chemical evolution is correct?

Accepted Answer

It refers to the formation of increasingly complex carbon-containing substances before biological evolution.

Question 11

Which of the following molecules would be considered hydrophobic?

Accepted Answer

Methane ($$CH_4)$$

Question 12

What is the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in pH and help maintain homeostasis.

Question 13

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

Accepted Answer

Chemical bonds range from equal sharing (nonpolar covalent) to unequal sharing (polar covalent) to complete transfer (ionic).

Question 14

Which of the following is true about carbon in biological molecules?

Accepted Answer

Carbon forms four covalent bonds due to its four valence electrons.

Question 15

A molecule of water ($$H_2O) is $$formed by which type of bond between hydrogen and oxygen?

Accepted Answer

Polar covalent bond

Question 16

Which of the following is a consequence of water's bent shape and polarity?

Accepted Answer

Water can form hydrogen bonds, leading to high cohesion and surface tension.

Question 17

Which of the following best describes an ion?

Accepted Answer

An atom or molecule that carries a charge due to loss or gain of electrons.

Question 18

Which of the following is the correct definition of molarity ($$M$$)?

Accepted Answer

$$M = 	ext{number of moles of solute per liter of solution}$$

Question 19

Which functional group is responsible for linking molecules together via disulfide bonds?

Accepted Answer

Sulthydryl group

Chpt. 2: Water and Carbon: The Chemical Basis of Life (General Biology Study Notes)

Study Guide - Practice Questions