Q: Which of the following is the correct formula for calculating the formal charge (FC) on an atom in a Lewis structure?

$$FC = \text{number of valence electrons} - \text{number of lone pair electrons} - \frac{1}{2}(\text{number of bonding electrons})$$

Q: Given the following bond energies: $$\text{H-H} = 436\ \text{kJ/mol}$$, $$\text{Cl-Cl} = 243\ \text{kJ/mol}$$, $$\text{H-Cl} = 431\ \text{kJ/mol}$$, calculate the enthalpy change ($$\Delta H_{rxn}) $$for the reaction: $$\text{H}_2 + \text{Cl}_2 \rightarrow 2\text{HCl}.$$

$$\Delta H_{rxn} = -184\ \text{kJ}$$

Q: Which of the following best explains why $$\text{NaCl} is a $$solid at room temperature while $$\text{HCl} is a $$gas?

$$\text{NaCl}$$ has strong ionic bonds, while $$\text{HCl}$$ has weaker covalent bonds.

Q: Which of the following is the correct order of increasing bond energy for the following bonds: $$\text{H-H}$$, $$\text{H-Cl}$$, $$\text{H-I}$$?

$$\text{H-I} \u003c \text{H-Cl} \u003c \text{H-H}$$

Question 1

Which of the following best describes the difference between ionic and covalent bonding, as illustrated by the Lewis structures for NaCl and HCl?

Accepted Answer

Ionic bonding involves the transfer of electrons to achieve noble gas configurations, while covalent bonding involves the sharing of electrons to achieve noble gas configurations.

Question 2

Which of the following statements about Lewis structures is correct?

Accepted Answer

Lewis structures represent the nucleus and core electrons with the chemical symbol, and valence electrons as dots around the symbol.

Question 3

Consider the molecule $$	ext{CO}_2. $$Which is the correct Lewis structure for this molecule?

Accepted Answer

$$:O=C=O:$$

Question 4

Which of the following molecules is an example of a molecule with an expanded valence shell?

Accepted Answer

$$	ext{SO}_4$$^{2-}$$

Question 5

Which of the following best explains why the bond angle in water ($$	ext{H}_2	ext{O}) is $$less than the ideal tetrahedral angle?

Accepted Answer

The lone pairs on oxygen repel the bonding pairs more strongly, compressing the bond angle.

Question 6

Which of the following is the correct formula for calculating the formal charge (FC) on an atom in a Lewis structure?

Accepted Answer

$$FC = 	ext{number of valence electrons} - 	ext{number of lone pair electrons} - \frac{1}{2}(	ext{number of bonding electrons})$$

Question 7

Which molecule below is expected to be polar based on its molecular geometry and dipole moments?

Accepted Answer

$$	ext{CHCl}_3$$

Question 8

Given the following bond energies: $$	ext{H-H} = 436\ 	ext{kJ/mol}$$, $$	ext{Cl-Cl} = 243\ 	ext{kJ/mol}$$, $$	ext{H-Cl} = 431\ 	ext{kJ/mol}$$, calculate the enthalpy change ($$\Delta H_{rxn}) $$for the reaction: $$	ext{H}_2 + 	ext{Cl}_2 ightarrow 2	ext{HCl}.$$

Accepted Answer

$$\Delta H_{rxn} = -184\ 	ext{kJ}$$

Question 9

Which of the following molecules is an example of a molecule with resonance structures?

Accepted Answer

$$	ext{O}_3$$

Question 10

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity decreases down a group and increases across a period.

Question 11

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

Accepted Answer

As bond order increases, bond length decreases.

Question 12

A molecule has three electron groups and one lone pair on the central atom. What is its molecular geometry according to VSEPR theory?

Accepted Answer

Bent

Question 13

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

Accepted Answer

$$	ext{BF}_3$$

Question 14

Which of the following best explains why $$	ext{NaCl} is a $$solid at room temperature while $$	ext{HCl} is a $$gas?

Accepted Answer

$$	ext{NaCl}$$ has strong ionic bonds, while $$	ext{HCl}$$ has weaker covalent bonds.

Question 15

Which of the following is the correct order of increasing bond energy for the following bonds: $$	ext{H-H}$$, $$	ext{H-Cl}$$, $$	ext{H-I}$$?

Accepted Answer

$$	ext{H-I} \u003c 	ext{H-Cl} \u003c 	ext{H-H}$$

Question 16

Which of the following molecules has a linear molecular geometry?

Accepted Answer

$$	ext{CO}_2$$

Question 17

Which of the following best describes a coordinate covalent bond?

Accepted Answer

A bond in which both electrons are donated by the same atom.

Question 18

Which of the following is the best description of a resonance structure?

Accepted Answer

A structure that represents one of two or more valid Lewis structures for a molecule that differ only in the arrangement of electrons.

Question 19

Which of the following is true about the percent ionic character of a bond as the electronegativity difference increases?

Accepted Answer

Percent ionic character increases.

Chemical Bonding I: Basic Concepts – Study Notes

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