Question 1

Which of the following best explains why ionic compounds do not have distinct molecular geometries like covalent compounds?

Accepted Answer

Ionic compounds form crystal lattices, which are repeating patterns of alternating positive and negative ions.

Question 2

What is the correct formula for lattice energy ($$U) of an $$ionic compound according to the notes?

Accepted Answer

$$U = \frac{Q_1$ Q_2$}{r}$$

Question 3

Which factor increases the lattice energy of an ionic compound?

Accepted Answer

Decreasing the size of the ions

Question 4

Given the following reactions, which compound has the highest lattice energy based on the provided enthalpy values?

$$\mathrm{Na} + \frac{1}{2} \mathrm{Cl}_2 \rightarrow \mathrm{NaCl} \qquad \Delta H = -411.12\ \mathrm{kJ/mol}$$

$$\mathrm{Ca} + \mathrm{O}_2 \rightarrow \mathrm{CaO} \qquad \Delta H = -635.09\ \mathrm{kJ/mol}$$

Accepted Answer

CaO

Question 5

Why do covalent network solids like diamond and SiO$$_2$$ have high melting points?

Accepted Answer

They are held together by strong covalent bonds in three dimensions.

Question 6

Which of the following compounds would you expect to have the lowest lattice energy?

Accepted Answer

NaCl

Question 7

If the ionic radius of an ion increases, what happens to the lattice energy of the ionic compound?

Accepted Answer

Lattice energy decreases

Question 8

Which statement best describes the bonding in covalent network solids?

Accepted Answer

Atoms are held together by covalent bonds in a continuous three-dimensional network.

Question 9

Which of the following is NOT an example of a covalent network solid?

Accepted Answer

NaCl

Question 10

A student claims that the crystal lattice structure of NaCl is due to covalent bonding. Which statement best refutes this claim?

Accepted Answer

NaCl forms a crystal lattice due to the electrostatic attraction between Na$$^+$$ and Cl$$^-$$ ions.

Question 11

Which of the following best describes the relationship between bond dissociation energy and lattice energy in ionic compounds?

Accepted Answer

Higher lattice energy corresponds to shorter and stronger ionic bonds.

Question 12

Which property is shared by both ionic compounds and covalent network solids?

Accepted Answer

They both form repeating patterns in a crystal lattice.

Question 13

Which of the following would most likely have the strongest bonds?

Accepted Answer

Covalent network solid like diamond

Question 14

Which of the following explains why SiO$$_2 is $$used in making windows?

Accepted Answer

SiO$$_2$$ forms a covalent network solid with strong bonds, making it hard and transparent.

Question 15

Which of the following would have the highest melting point?

Accepted Answer

Al$$_2O$_3$$

Question 16

Which of the following is a direct consequence of the crystal lattice structure in ionic compounds?

Accepted Answer

High melting and boiling points

Question 17

Which of the following best describes the role of atomic radius in determining lattice energy?

Accepted Answer

Smaller atomic radius leads to higher lattice energy due to closer ion packing.

Question 18

Which compound would you expect to have the lowest solubility in water due to its strong lattice energy?

Accepted Answer

Al$$_2O$_3$$

Question 19

Which of the following statements is true about the structure of diamond?

Accepted Answer

Diamond consists of carbon atoms covalently bonded in a three-dimensional network.

Question 20

Which of the following is the best explanation for why ionic compounds are brittle?

Accepted Answer

Shifting layers in the crystal lattice brings like charges together, causing repulsion and fracture.

Ionic Compounds, Crystal Lattices, and Covalent Network Solids

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