Question 1

Which of the following statements best describes the difference between a covalent bond and a coordinative covalent bond?

Accepted Answer

In a covalent bond, both atoms contribute one electron each to the bond, while in a coordinative covalent bond, both electrons come from the same atom.

Question 2

Which of the following molecules is expected to have the largest dipole moment based on its molecular geometry and electronegativity differences?

Accepted Answer

HCl

Question 3

Given the following Lewis structure for the nitrite ion, $$\mathrm{NO_2$^-}$$, what is the formal charge on the central nitrogen atom?

$$\mathrm{O=N-O^-}$$

Accepted Answer

$$+1$$

Question 4

Which of the following molecules violates the octet rule by having an incomplete octet?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 5

What is the bond order of the carbonate ion, $$\mathrm{CO_3$^{2-}}$$, based on its resonance structures?

Accepted Answer

$$1.33$$

Question 6

Which of the following best explains why $$\mathrm{H_2O} is a $$polar molecule while $$\mathrm{CO_2$} is $$nonpolar, even though both contain polar bonds?

Accepted Answer

The molecular geometry of $$\mathrm{H_2O} is $$bent, causing the dipoles to add, while $$\mathrm{CO_2$} is $$linear, causing the dipoles to cancel.

Question 7

Which of the following molecules has a trigonal planar molecular geometry?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 8

Calculate the enthalpy change $$\Delta H_{rxn}$$ for the reaction $$\mathrm{H_2$(g) + Cl_2$(g) \rightarrow 2HCl(g)}$$ using the following bond energies:

$$\mathrm{H-H}$$: $$436\ \mathrm{kJ/mol}$$
$$\mathrm{Cl-Cl}$$: $$243\ \mathrm{kJ/mol}$$
$$\mathrm{H-Cl}$$: $$431\ \mathrm{kJ/mol}$$

Accepted Answer

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

Question 9

Which of the following statements about resonance structures is correct?

Accepted Answer

The actual structure is a hybrid of all resonance forms and does not oscillate between them.

Question 10

Which of the following ions has an expanded valence shell?

Accepted Answer

$$\mathrm{SF_6$}$$

Question 11

What is the ideal bond angle in a molecule with tetrahedral electron-group geometry?

Accepted Answer

$$109.5^\circ$$

Question 12

Which of the following best describes the trend in electronegativity across a period in the periodic table?

Accepted Answer

Electronegativity increases from left to right across a period.

Question 13

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

Accepted Answer

$$\mathrm{$$CCl_4$$}$$

Question 14

What is the formal charge on the oxygen atom in the Lewis structure of water, $$\mathrm{H_2O}$$?

Accepted Answer

$$0$$

Question 15

Which of the following best explains why $$\mathrm{NaCl} is an $$ionic compound while $$\mathrm{Cl_2$} is a $$covalent compound?

Accepted Answer

The electronegativity difference between Na and Cl is large, leading to electron transfer, while in $$\mathrm{Cl_2$}$$ the atoms share electrons equally.

Question 16

Which of the following molecules has a bond angle closest to $$120^\circ$$?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 17

Which of the following is the correct Lewis symbol for sulfur (S)?

Accepted Answer

A chemical symbol S with six dots around it.

Question 18

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

Accepted Answer

As bond order increases, bond length decreases.

Question 19

Which of the following molecules or ions has a linear molecular geometry?

Accepted Answer

$$\mathrm{CO_2$}$$

Question 20

Which of the following is a correct application of the octet rule when drawing Lewis structures?

Accepted Answer

Hydrogen atoms are always terminal and require only two electrons.

Chemical Bonding I: Lewis Structures, Electronegativity, and Molecular Geometry

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