Question 1

Which of the following statements best explains why water is an excellent solvent for ionic compounds?

Accepted Answer

Water molecules have both slight positive and negative charges, allowing them to surround and separate ions.

Question 2

A carbon atom has an atomic number of 6 and a mass number of 14. How many neutrons does this atom have?

Accepted Answer

$$14 - 6 = 8$$ neutrons

Question 3

Which property of water allows it to move upward through the roots and stems of plants against gravity?

Accepted Answer

Cohesion due to hydrogen bonding

Question 4

What is the main reason ice floats on liquid water?

Accepted Answer

Hydrogen bonds in ice create an open lattice structure, making ice less dense than liquid water.

Question 5

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electrons between atoms.

Question 6

A sodium atom (Na) has 11 protons and 12 neutrons. What is its mass number?

Accepted Answer

$$11 + 12 = 23$$

Question 7

Which statement about valence electrons is correct?

Accepted Answer

Valence electrons are the electrons in the outermost shell and are involved in chemical bonding.

Question 8

Why do water molecules have a bent shape?

Accepted Answer

Because the shared electrons are pulled toward the oxygen atom, creating a partial negative charge and repelling the hydrogen atoms.

Question 9

Which of the following is a consequence of water's high specific heat for living organisms?

Accepted Answer

Water absorbs and releases heat slowly, helping to stabilize temperatures in organisms and environments.

Question 10

A chlorine atom has 17 protons and 18 neutrons. What is its atomic number and mass number?

Accepted Answer

Atomic number: $$17$$, Mass number: $$35$$

Question 11

Which of the following best explains why nonpolar molecules do not dissolve in water?

Accepted Answer

Nonpolar molecules do not form hydrogen bonds with water, so they are not surrounded and separated by water molecules.

Question 12

Which of the following is true about isotopes?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 13

Which of the following molecules is most likely to form hydrogen bonds with water?

Accepted Answer

Ammonia ($$NH_3)$$

Question 14

If an atom has 8 electrons, how many electrons will be in its outer shell according to the octet rule?

Accepted Answer

8 electrons

Question 15

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

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, while nonpolar covalent bonds involve equal sharing.

Question 16

Which property of water is most important for maintaining the structure of biological macromolecules?

Accepted Answer

Water's ability to form hydrogen bonds

Question 17

A molecule of water ($$H_2O) is $$described as polar. What does this mean?

Accepted Answer

The molecule has a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom.

Question 18

Which of the following is a direct result of water's surface tension?

Accepted Answer

Small insects can walk on the surface of water without sinking.

Question 19

Which of the following elements is most likely to form four covalent bonds in organic molecules?

Accepted Answer

Carbon

Question 20

Which of the following best explains why water stabilizes temperature in living organisms?

Accepted Answer

Water has a high specific heat, so it absorbs and releases heat slowly.

Atoms, Ions, Molecules, and Water: Foundations of Chemical Evolution in Biology

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