Question 1

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

Accepted Answer

Water molecules are polar, so their partial positive and negative charges can surround and stabilize ions in solution.

Question 2

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

Accepted Answer

$$8$$

Question 3

Which property of water is primarily responsible for the ability of plants to transport water from their roots to their leaves against gravity?

Accepted Answer

Water's cohesive and adhesive properties due to hydrogen bonding

Question 4

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electron pairs between atoms

Question 5

If an atom has 11 protons, 12 neutrons, and 11 electrons, what is its atomic mass?

Accepted Answer

$$23$$

Question 6

Why does ice float on liquid water?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds hold water molecules further apart in a solid state.

Question 7

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 8

A sodium atom (Na) loses one electron to become a sodium ion (Na$$^+). $$What is the resulting charge and why?

Accepted Answer

The sodium ion has a positive charge because it lost a negatively charged electron.

Question 9

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

Accepted Answer

Hydrogen bonds between water molecules require more energy to break, so water can absorb more heat before its temperature rises.

Question 10

Which of the following statements about valence electrons is correct?

Accepted Answer

Valence electrons are the electrons available for forming chemical bonds in the outermost shell.

Question 11

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

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, resulting in partial charges, while nonpolar covalent bonds involve equal sharing.

Question 12

A molecule of methane (CH$$_4) $$contains how many covalent bonds?

Accepted Answer

$$4$$

Question 13

Which of the following is a direct consequence of water's polarity?

Accepted Answer

Water can dissolve both ionic and polar substances easily.

Question 14

Which of the following best explains why carbon is able to form large, complex molecules?

Accepted Answer

Carbon can form four covalent bonds due to its four valence electrons.

Question 15

Which of the following scenarios best illustrates the concept of surface tension in water?

Accepted Answer

A paperclip floating on the surface of water due to the cohesive forces among water molecules.

Question 16

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

Hydrogen bonds form between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 17

If an atom has an atomic number of 9 and a mass number of 19, how many neutrons does it have?

Accepted Answer

$$10$$

Question 18

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

Accepted Answer

Water absorbs and releases heat slowly due to hydrogen bonding, minimizing temperature fluctuations.

Question 19

Which of the following is an example of an organic functional group that contains nitrogen?

Accepted Answer

Amino group ($$-NH_2$)

Question 20

A molecule has the formula $$C_2H_6O. $$Which of the following best describes its structure?

Accepted Answer

It contains two carbon atoms, six hydrogen atoms, and one oxygen atom, and could be either ethanol or dimethyl ether.

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

Study Guide - Practice Questions