Q: Which of the following is the correct formula for calculating formal charge?

$$\text{Formal charge} = \text{Valence electrons} - (\text{Nonbonding electrons} + \frac{1}{2}\text{Bonding electrons})$$

Question 1

Which of the following best describes the octet rule as it applies to chemical bonding?

Accepted Answer

Atoms tend to gain, lose, or share electrons to achieve eight electrons in their valence shell.

Question 2

Which molecule below has a central atom with a formal charge of zero?

Accepted Answer

In $$\mathrm{CO_2$}$$, the central carbon atom has a formal charge of zero.

Question 3

Given the following bond energies: $$\mathrm{H-H} = 436 kJ/$$mol, $$\mathrm{Cl-Cl} = 242 kJ/$$mol, $$\mathrm{H-Cl} = 431 kJ/$$mol, what is the enthalpy change ($$\Delta H) $$for the reaction $$\mathrm{H_2$ + Cl_2$ \rightarrow 2HCl}$$?

Accepted Answer

$$\Delta H = -184 kJ/$$mol

Question 4

Which of the following Lewis Dot Structures correctly represents the bonding in $$\mathrm{O_3$} ($$ozone)?

Accepted Answer

A resonance structure with one double bond and one single bond, and formal charges of +1, 0, and -1 on the oxygen atoms.

Question 5

Which statement about formal charge is correct?

Accepted Answer

Formal charge helps identify the most stable Lewis structure by minimizing charges on atoms.

Question 6

A student draws the Lewis structure for $$\mathrm{NO_2$^-}$$ and assigns formal charges. What is the formal charge on the nitrogen atom?

Accepted Answer

0

Question 7

Which of the following best explains why $$\mathrm{$$CCl_4$$} is $$nonpolar despite having polar bonds?

Accepted Answer

The molecule is tetrahedral and the bond dipoles cancel out due to symmetry.

Question 8

Which of the following is the correct formula for calculating formal charge?

Accepted Answer

$$	ext{Formal charge} = 	ext{Valence electrons} - (	ext{Nonbonding electrons} + \frac{1}{2}	ext{Bonding electrons})$$

Question 9

Which molecule below violates the octet rule?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 10

In the reaction $$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$, use the following bond energies: $$\mathrm{C-H} = 413 kJ/$$mol, $$\mathrm{O=O} = 498 kJ/$$mol, $$\mathrm{C=O} = 799 kJ/$$mol, $$\mathrm{O-H} = 463 kJ/$$mol. What is the approximate enthalpy change ($$\Delta H) $$for the reaction?

Accepted Answer

$$\Delta H = -802 kJ/$$mol

Question 11

Which of the following statements about resonance structures is correct?

Accepted Answer

Resonance structures represent delocalized electrons and the true structure is a hybrid of all possible forms.

Question 12

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

Accepted Answer

Higher bond energy corresponds to a stronger bond.

Question 13

A patient is exposed to carbon monoxide ($$\mathrm{CO}). $$Which feature of the $$\mathrm{CO}$$ molecule makes it dangerous in the body?

Accepted Answer

$$\mathrm{CO}$$ forms a very strong bond with hemoglobin due to its triple bond and lone pair, preventing oxygen transport.

Question 14

Which of the following is NOT a valid Lewis Dot Structure for $$\mathrm{SO_2$}$$?

Accepted Answer

A structure with two double bonds and no formal charges.

Question 15

Which of the following statements about bond energy calculations is correct?

Accepted Answer

The enthalpy change ($$\Delta H) $$for a reaction is calculated as the sum of bond energies of bonds broken minus the sum of bond energies of bonds formed.

Question 16

Which of the following molecules has a central atom with an expanded octet?

Accepted Answer

$$\mathrm{$$PCl_5$$}$$

Question 17

In the Lewis structure of $$\mathrm{H_2SO_4}$$, what is the formal charge on the sulfur atom?

Accepted Answer

0

Question 18

Which of the following best explains why $$\mathrm{N_2$}$$ has a very high bond energy?

Accepted Answer

$$\mathrm{N_2$}$$ contains a triple bond, which requires breaking three pairs of shared electrons.

Question 19

Which of the following is a correct application of formal charge in predicting the most likely Lewis structure for $$\mathrm{NO_3$^-}$$?

Accepted Answer

The most likely structure minimizes formal charges, placing the -1 charge on an oxygen atom.

Chemical Bonding: Lewis Structures, Formal Charge, and Bond Energies

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