AP Chemistry Questions on Covalent Bond Length and Strength

📚 Quick Study Guide

• 📏 Bond Length: The distance between the nuclei of two bonded atoms. Shorter bond length usually means stronger bond.
• 💪 Bond Strength (Bond Dissociation Energy): The energy required to break one mole of bonds in the gaseous phase. Higher bond energy means stronger bond.
• ⚛️ Factors Affecting Bond Length and Strength:
  • Atomic Size: Larger atoms generally form longer (and thus weaker) bonds.
  • Bond Order: Single bonds are longer and weaker than double bonds, which are longer and weaker than triple bonds.
  • Electronegativity: Differences in electronegativity can influence bond polarity and, to a lesser extent, bond strength.
• 🧪 Relationship: Shorter bonds are generally stronger because the electrons are held more closely to the nuclei, leading to greater electrostatic attraction.
• 📝 Formulas to Remember: While there isn't a direct formula, understanding trends is key. Bond order is calculated as: $\frac{Number\,of\,bonding\,electrons - Number\,of\,antibonding\,electrons}{2}$

🧪 Practice Quiz

1. Which of the following bonds is the longest?
   1. C-C
   2. C=C
   3. C≡C
   4. C-H
2. Which of the following bonds is the strongest?
   1. N-N
   2. N=N
   3. N≡N
   4. N-H
3. As the bond order increases, the bond length:
   1. Increases
   2. Decreases
   3. Remains the same
   4. Fluctuates randomly
4. Which of the following molecules has the shortest bond length between the two carbon atoms?
   1. Ethane ($C_2H_6$)
   2. Ethene ($C_2H_4$)
   3. Ethyne ($C_2H_2$)
   4. All have the same bond length
5. Which of the following factors does NOT significantly affect bond strength?
   1. Atomic size
   2. Bond order
   3. Electronegativity
   4. State of matter
6. Compared to a single bond, a double bond is:
   1. Longer and weaker
   2. Shorter and weaker
   3. Longer and stronger
   4. Shorter and stronger
7. Which bond requires the most energy to break?
   1. Single bond
   2. Double bond
   3. Triple bond
   4. Ionic bond