Question 1

Which of the following statements best explains why ionic compounds, such as NaCl, have high melting points?

Accepted Answer

Because the ions are held together by strong electrostatic attractions in a well-defined three-dimensional lattice.

Question 2

According to the octet rule, atoms tend to gain, lose, or share electrons until they are surrounded by how many valence electrons?

Accepted Answer

Eight

Question 3

Which of the following best describes the process of ionic bonding between sodium and chlorine?

Accepted Answer

Sodium loses an electron to form $\mathrm{Na^+}$ and chlorine gains an electron to form $\mathrm{Cl^-}$.

Question 4

Which of the following is NOT a property of ionic substances?

Accepted Answer

They are malleable and ductile.

Question 5

The lattice energy of an ionic compound is defined as:

Accepted Answer

The energy required to completely separate one mole of a solid ionic compound into its gaseous ions.

Question 6

Which factor increases the lattice energy of an ionic compound?

Accepted Answer

Increasing the charge on the ions.

Question 7

Which statement about the electron configuration of ions is correct?

Accepted Answer

Main group metals lose electrons to achieve the electron configuration of the previous noble gas.

Question 8

Which of the following molecules contains a triple bond?

Accepted Answer

$\mathrm{N_2}$

Question 9

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally between two atoms, resulting in partial charges.

Question 10

Electronegativity generally increases as you move:

Accepted Answer

From left to right across a period and from bottom to top of a group.

Question 11

A dipole moment ($\mu$) is produced when:

Accepted Answer

Two electrical charges of equal magnitude but opposite sign are separated by a distance.

Question 12

Which of the following compounds is most likely to have ionic bonding?

Accepted Answer

$\mathrm{LiF}$

Question 13

When drawing Lewis structures, what is the purpose of assigning formal charges?

Accepted Answer

To determine the most stable structure by minimizing formal charges and placing negative charges on the most electronegative atoms.

Question 14

Which of the following molecules is an example of a resonance structure?

Accepted Answer

Ozone ($\mathrm{O_3}$)

Question 15

Which of the following is an exception to the octet rule?

Accepted Answer

Molecules with an odd number of electrons, such as $\mathrm{NO}$.

Question 16

Which element can have an expanded octet in its compounds?

Accepted Answer

Phosphorus

Question 17

Which statement about bond strength and bond length is correct?

Accepted Answer

As the number of bonds between two atoms increases, the bond length decreases and the bond strength increases.

Question 18

Calculate the enthalpy change ($\Delta H$) for the reaction $\mathrm{CH_4 (g) + Cl_2 (g) \rightarrow CH_3Cl (g) + HCl (g)}$ using the following average bond enthalpies: $D(C-H) = 413\ \mathrm{kJ/mol}$, $D(Cl-Cl) = 242\ \mathrm{kJ/mol}$, $D(C-Cl) = 328\ \mathrm{kJ/mol}$, $D(H-Cl) = 431\ \mathrm{kJ/mol}$.

Accepted Answer

$\Delta H = -104\ \mathrm{kJ}$

Question 19

Which of the following best explains why $\mathrm{BF_3}$ does not obey the octet rule?

Accepted Answer

Boron in $\mathrm{BF_3}$ has fewer than eight electrons, and filling its octet would place a negative formal charge on boron and a positive charge on fluorine.

Basic Concepts of Chemical Bonding

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