Chemical Bonding — Practice Quiz

A Chemistry cheat sheet for Chemical Bonding — every key formula with its symbols defined — plus a medium-level practice quiz to test recall.

Practice quiz

1. Calculate the electrostatic potential energy between two ions, $Q_1 = +2e$ and $Q_2 = -1e$, separated by a distance of $0.25 \text{ nm}$. Use $k = 8.99 \times 10^9 \text{ J} \cdot \text{m/C}^2$ and $e = 1.602 \times 10^{-19} \text{ C}$.

   • $-1.84 \times 10^{-18} \text{ J}$
   • $1.84 \times 10^{-18} \text{ J}$
   • $-3.68 \times 10^{-18} \text{ J}$
   • $3.68 \times 10^{-18} \text{ J}$

   Answer: $-1.84 \times 10^{-18} \text{ J}$

2. How does the electrostatic potential energy $E_{\text{el}}$ between two oppositely charged ions change if the distance $d$ between them is doubled?

   • It becomes half as negative (closer to zero).
   • It becomes twice as negative.
   • It remains the same.
   • It becomes four times as negative.

   Answer: It becomes half as negative (closer to zero).

3. A molecule has a charge separation of $1.5 \times 10^{-19} \text{ C}$ and the distance between the separated charges is $1.2 \text{ \AA}$. Calculate its dipole moment $\mu$.

   • $1.8 \times 10^{-29} \text{ C} \cdot \text{m}$
   • $1.8 \times 10^{-30} \text{ C} \cdot \text{m}$
   • $1.25 \times 10^{-9} \text{ C} \cdot \text{m}$
   • $1.25 \times 10^{-10} \text{ C} \cdot \text{m}$

   Answer: $1.8 \times 10^{-29} \text{ C} \cdot \text{m}$

4. Which of the following factors would lead to an increase in the dipole moment $\mu$ of a diatomic molecule?

   • Decreasing the magnitude of the separated charges.
   • Increasing the distance between the separated charges.
   • Making the molecule more symmetrical.
   • Decreasing the electronegativity difference between the atoms.

   Answer: Increasing the distance between the separated charges.

5. Estimate the enthalpy change $\Delta H_{\text{rxn}}$ for the reaction: $2\text{H}_2(\text{g}) + \text{O}_2(\text{g}) \rightarrow 2\text{H}_2\text{O}(\text{g})$ using the provided average bond enthalpies. (H-H: $436 \text{ kJ/mol}$, O=O: $495 \text{ kJ/mol}$, O-H: $463 \text{ kJ/mol}$)

   • $-485 \text{ kJ/mol}$
   • $485 \text{ kJ/mol}$
   • $-242.5 \text{ kJ/mol}$
   • $242.5 \text{ kJ/mol}$

   Answer: $-485 \text{ kJ/mol}$

6. The formula for $\Delta H_{\text{rxn}}$ using bond enthalpies is most accurate for which type of reactions?

   • Reactions involving solids and liquids.
   • Reactions occurring in aqueous solutions.
   • Gas-phase reactions.
   • Reactions at very low temperatures.

   Answer: Gas-phase reactions.

7. According to the provided Lewis Symbols table, which of the following is the correct Lewis symbol for a Nitrogen atom?

   • :N::\cdot
   • :N::
   • \cdot N \cdot
   • :N:

   Answer: :N::\cdot

8. What is the bond order for the carbon-oxygen bond in carbon monoxide, $\text{CO}$?

   • $1$
   • $2$
   • $3$
   • $2.5$

   Answer: $3$

9. Based on the provided tables, which statement is true regarding carbon-carbon bonds?

   • A $\text{C-C}$ single bond is stronger and shorter than a $\text{C=C}$ double bond.
   • A $\text{C=C}$ double bond is stronger and shorter than a $\text{C\equiv C}$ triple bond.
   • A $\text{C\equiv C}$ triple bond is stronger and shorter than a $\text{C=C}$ double bond.
   • All carbon-carbon bonds have approximately the same strength and length.

   Answer: A $\text{C\equiv C}$ triple bond is stronger and shorter than a $\text{C=C}$ double bond.

10. Consider the $\text{C-O}$ bond. How does its bond enthalpy and bond length compare to a $\text{C=O}$ bond?

    • $\text{C-O}$ has a higher bond enthalpy and a shorter bond length than $\text{C=O}$.
    • $\text{C-O}$ has a lower bond enthalpy and a longer bond length than $\text{C=O}$.
    • $\text{C-O}$ has a higher bond enthalpy and a longer bond length than $\text{C=O}$.
    • $\text{C-O}$ has a lower bond enthalpy and a shorter bond length than $\text{C=O}$.

    Answer: $\text{C-O}$ has a lower bond enthalpy and a longer bond length than $\text{C=O}$.