Question 1

Which of the following atoms is most likely to form four covalent bonds in biological molecules, and why?

Accepted Answer

Carbon, because it has 4 unpaired electrons in its valence shell.

Question 2

A solution with a pH of 3 is considered acidic. What does this indicate about the concentration of $$\mathrm{H^+}$$ ions in the solution?

Accepted Answer

It has a high concentration of $$\mathrm{H^+}$$ ions.

Question 3

Which property of water allows insects to walk on its surface, and what is the molecular basis for this property?

Accepted Answer

Surface tension, caused by cohesive forces among water molecules at the surface.

Question 4

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally, resulting in partial charges on the atoms.

Question 5

If an oxygen atom has an atomic number of 8 and a mass number of 16, how many neutrons does it have?

Accepted Answer

8

Question 6

Which statement best explains why water is a good solvent for ionic and polar substances?

Accepted Answer

Water molecules have partial positive and negative charges that interact with ions and polar molecules.

Question 7

What is the difference between a cation and an anion?

Accepted Answer

A cation has a full positive charge, while an anion has a full negative charge.

Question 8

Which of the following best describes the concept of electronegativity?

Accepted Answer

The amount of strength an element has in pulling the shared electron towards itself in a bond.

Question 9

A molecule is described as hydrophilic. What does this mean about its chemical properties?

Accepted Answer

It interacts readily with water and is typically polar or charged.

Question 10

Which of the following is true about the valence electrons in carbon?

Accepted Answer

Carbon has 4 unpaired electrons in its valence shell.

Question 11

Which of the following functional groups is found in all amino acids and is responsible for their basic properties?

Accepted Answer

Amino group ($$\mathrm{-NH_2$})$$

Question 12

In the chemical reaction $$\mathrm{C + O_2$ \rightarrow CO_2$}$$, which molecule is the reactant and which is the product?

Accepted Answer

Reactant: $$\mathrm{C}$$ and $$\mathrm{O_2$}$$; Product: $$\mathrm{CO_2$}$$

Question 13

Which property of water explains why ice floats on liquid water?

Accepted Answer

Ice is less dense than liquid water due to hydrogen bonding.

Question 14

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

Accepted Answer

Acids give up protons during a reaction.

Question 15

How many electrons can the innermost electron shell of an atom hold?

Accepted Answer

2

Question 16

Which of the following best explains why methane ($$\mathrm{CH_4$}) $$has a tetrahedral shape?

Accepted Answer

The repulsive forces between the negative charges in shared and unshared electron pairs in the valence shell.

Question 17

Which of the following is a correct definition of a covalent bond?

Accepted Answer

A type of chemical bond in which two atoms share one or more pairs of electrons.

Question 18

Which of the following molecules is most likely to be hydrophobic?

Accepted Answer

A molecule with no charge and mostly nonpolar covalent bonds.

Question 19

Which property of water is most important for regulating Earth's climate by absorbing heat?

Accepted Answer

High specific heat

Question 20

Which of the following statements about the structure of a water molecule is correct?

Accepted Answer

The oxygen atom has a partial negative charge, while the hydrogen atoms have partial positive charges.

Atoms, Ions, Molecules, and Water: Foundations of General Biology

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