Question 1

Which of the following molecules is an example of a compound that violates the octet rule due to an expanded octet?

Accepted Answer

$$\mathrm{SF_6$}$$

Question 2

Which of the following statements best explains why $$\mathrm{O_3$} ($$ozone) exhibits resonance?

Accepted Answer

The actual structure is a hybrid of two or more valid Lewis structures differing only in the placement of electrons.

Question 3

Given the following bond energies: $$\mathrm{H-H}$$: $$436\ \mathrm{kJ/mol}$$, $$\mathrm{Cl-Cl}$$: $$243\ \mathrm{kJ/mol}$$, $$\mathrm{H-Cl}$$: $$431\ \mathrm{kJ/mol}$$, estimate $$\Delta H_{rxn}$$ for the reaction $$\mathrm{H_2$} + \mathrm{Cl_2$} \rightarrow 2\mathrm{HCl}.$$

Accepted Answer

$$-184\ \mathrm{kJ}$$

Question 4

Which of the following molecules is nonpolar, despite having polar bonds?

Accepted Answer

$$\mathrm{CO_2$}$$

Question 5

What is the molecular geometry and approximate bond angle of $$\mathrm{BF_3$}$$ according to VSEPR theory?

Accepted Answer

Trigonal planar, $$120^\circ$$

Question 6

Which of the following best describes the hybridization of the central atom in $$\mathrm{$$PCl_5$$}$$?

Accepted Answer

$$sp^3d$

Question 7

How many sigma ($$\sigma) $$and pi ($$\pi) $$bonds are present in the molecule $$\mathrm{C_2H_4} ($$ethylene)?

Accepted Answer

5 $$\sigma$$, 1 $$\pi$$

Question 8

Which of the following molecules has a bond order of 2 according to molecular orbital theory?

Accepted Answer

$$\mathrm{O_2$}$$

Question 9

Which intermolecular force is primarily responsible for the high boiling point of water compared to other group 16 hydrides?

Accepted Answer

Hydrogen bonding

Question 10

A sample of solid carbon dioxide ($$\mathrm{CO_2$}$$, dry ice) is left on a table at room temperature. Which phase change occurs, and what is the name of this process?

Accepted Answer

Solid to gas; sublimation

Question 11

Which of the following statements about vapor pressure is correct?

Accepted Answer

Vapor pressure increases as temperature increases.

Question 12

Which of the following molecules has a seesaw molecular geometry?

Accepted Answer

$$\mathrm{SF_4$}$$

Question 13

What is the formal charge on the central atom in the best Lewis structure for $$\mathrm{NO_3$^-}$$?

Accepted Answer

0

Question 14

Which of the following best describes the electron geometry and molecular geometry of $$\mathrm{H_2O}$$?

Accepted Answer

Electron geometry: tetrahedral; Molecular geometry: bent

Question 15

Which of the following molecules is paramagnetic according to molecular orbital theory?

Accepted Answer

$$\mathrm{O_2$}$$

Question 16

Which of the following best explains why $$\mathrm{NH_3$} is $$polar?

Accepted Answer

It has a trigonal pyramidal shape with a lone pair on nitrogen, resulting in a net dipole moment.

Question 17

Which of the following phase changes is exothermic?

Accepted Answer

Condensation

Question 18

What is the hybridization of the carbon atom in carbon dioxide ($$\mathrm{CO_2$}$$)?

Accepted Answer

$$sp$$

Question 19

Which of the following best describes the relationship between bond order and bond strength?

Accepted Answer

As bond order increases, bond strength increases.

Question 20

A phase diagram for a substance shows a point where the solid, liquid, and gas phases coexist in equilibrium. What is this point called?

Accepted Answer

Triple point

Chemical Bonding, Molecular Structure, and Intermolecular Forces

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