Question 1

Which of the following statements best explains why ice floats on water, and why this property is important for aquatic life?

Accepted Answer

Ice is less dense than liquid water due to hydrogen bonds, which allows it to float and insulate aquatic organisms below from freezing temperatures.

Question 2

A neutral atom of sodium (Na) has an atomic number of 11. How many electrons are in its outermost shell, and what is the significance of this for chemical bonding?

Accepted Answer

1 electron; this makes sodium highly reactive and likely to donate this electron to achieve a stable configuration.

Question 3

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

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, often resulting in hydrophilic molecules, while nonpolar covalent bonds involve equal sharing and are usually hydrophobic.

Question 4

A solution has a pH of 4. Another solution has a pH of 7. How many times greater is the hydrogen ion concentration in the first solution compared to the second?

Accepted Answer

$$10^3 = 1$$,000$$

Question 5

Which of the following is NOT a property shared by all living things?

Accepted Answer

Ability to photosynthesize

Question 6

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

Accepted Answer

Hydrogen bonds between water molecules absorb heat, allowing water to resist temperature changes.

Question 7

Which of the following statements about organic molecules is correct?

Accepted Answer

Organic molecules must have a carbon backbone and at least one carbon-hydrogen (C-H) bond.

Question 8

Which macromolecule is primarily responsible for storing genetic information, and what is its monomer?

Accepted Answer

Nucleic acids; nucleotide

Question 9

A patient is diagnosed with a genetic disorder caused by a single amino acid change in a protein. Which property of proteins does this most directly affect?

Accepted Answer

The three-dimensional shape of the protein, which determines its function.

Question 10

Which of the following best describes the structure and function of phospholipids in the plasma membrane?

Accepted Answer

They form a bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward, creating a selective barrier.

Question 11

Which of the following is an example of an ionic bond?

Accepted Answer

The bond between sodium (Na) and chlorine (Cl) in table salt (NaCl), where one atom donates an electron to another.

Question 12

Which of the following best explains why nonpolar covalent molecules like methane (CH4) do not dissolve in water?

Accepted Answer

They are hydrophobic due to equal sharing of electrons, so they do not interact favorably with water's polar molecules.

Question 13

A solution has a pH of 2. What is the hydrogen ion concentration $$[H^+] of $$this solution?

Accepted Answer

$$[H^+] = 10$$^{-2}$$ = 0.01$$\,mol/L

Question 14

Which of the following best describes the role of carbohydrates in living organisms?

Accepted Answer

They serve as a primary energy source for most organisms.

Question 15

Which of the following statements about acids and bases is correct?

Accepted Answer

An acid increases the $$[H^+]$$ concentration in a solution, while a base decreases it.

Question 16

Which of the following is a correct statement about the atomic structure of carbon (C), atomic number 6?

Accepted Answer

It has 4 valence electrons, allowing it to form up to 4 covalent bonds.

Question 17

Which of the following best explains why the pH scale is logarithmic?

Accepted Answer

Each unit change in pH represents a tenfold change in hydrogen ion concentration.

Question 18

Which of the following is NOT a function of proteins in living organisms?

Accepted Answer

Long-term energy storage

Question 19

A scientist discovers a molecule with a carbon backbone and several C-H bonds. Which class of biological molecule does this most likely belong to?

Accepted Answer

Organic molecule

Question 20

Which of the following best describes the relationship between protons, neutrons, and electrons in a neutral atom?

Accepted Answer

The number of protons equals the number of electrons, and the atomic mass is the sum of protons and neutrons.

The Chemistry of Life: Study Guide for General Biology

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