AP Chemistry Flashcards: Bond Enthalpies

What this deck covers

This deck focuses on Bond Enthalpies, giving you a quick way to review the definitions, rules, and examples that matter most for AP Chemistry.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the bond enthalpy of a C-H bond in kJ/mol?

Answer: Approximately 413 kJ/mol. Common value for single C-H bonds in organic molecules.

Flashcard 2: What is the bond enthalpy of a C=O bond in carbon dioxide?

Answer: 799 kJ/mol. Strong double bond in carbon dioxide molecule.

Flashcard 3: What is the bond enthalpy of an N-H bond?

Answer: 391 kJ/mol. Standard value for nitrogen-hydrogen single bonds.

Flashcard 4: What is the bond enthalpy of an F-F bond?

Answer: 157 kJ/mol. Weak bond due to lone pair repulsion between fluorines.

Flashcard 5: Which bond typically has a higher bond enthalpy: C=C or C-C?

Answer: C=C. Double bonds are stronger than single bonds.

Flashcard 6: What is the definition of bond enthalpy?

Answer: The energy required to break one mole of a bond in gaseous molecules. Always measured for gaseous species at standard conditions.

Flashcard 7: What is the bond enthalpy of an O=O bond?

Answer: 498 kJ/mol. Strong double bond between oxygen atoms in $O_2$.

Flashcard 8: Compare bond enthalpies: O-H vs C-H.

Answer: O-H > C-H. O-H bond (463) is stronger than C-H bond (413).

Flashcard 9: Identify the bond with the highest bond enthalpy: C-H, N≡N, O=O.

Answer: N≡N. N≡N has the highest enthalpy due to triple bonding.

Flashcard 10: What happens to bond enthalpy as bond length increases?

Answer: Bond enthalpy decreases. Longer bonds have weaker attractive forces between atoms.

Flashcard 11: What is the bond enthalpy of a C=O bond in carbon dioxide?

Answer: 799 kJ/mol. Strong double bond in carbon dioxide molecule.

Flashcard 12: What is the bond enthalpy of an N-H bond?

Answer: 391 kJ/mol. Standard value for nitrogen-hydrogen single bonds.

Flashcard 13: What does a negative enthalpy change indicate about a reaction?

Answer: The reaction is exothermic. Energy is released to the surroundings during reaction.

Flashcard 14: Calculate the bond enthalpy change for breaking 2 Cl-Cl and forming 2 Cl-H. Use 242 and 431 kJ/mol.

Answer: $\Delta H = 2(242) - 2(431) = -378 \text{ kJ/mol}$. Breaking uses 484 kJ/mol, forming releases 862 kJ/mol.

Flashcard 15: Calculate the bond enthalpy change: breaking 2 H-H and forming 2 H-O. Use 436 kJ/mol (H-H) and 463 kJ/mol (H-O).

Answer: $\Delta H = 2(436) - 2(463) = -54 \text{ kJ/mol}$. Breaking requires 872 kJ/mol, forming releases 926 kJ/mol.

Flashcard 16: What is the bond enthalpy of an O-H bond?

Answer: 463 kJ/mol. Standard value for oxygen-hydrogen bonds in water.

Flashcard 17: Calculate the enthalpy change: breaking H-H and Cl-Cl, forming 2 H-Cl. Use 436, 242, and 431 kJ/mol.

Answer: $\Delta H = (436 + 242) - 2(431) = -184 \text{ kJ/mol}$. Breaking uses 678 kJ/mol, forming releases 862 kJ/mol.

Flashcard 18: What is the bond enthalpy of a N=N bond?

Answer: 418 kJ/mol. Standard value for nitrogen-nitrogen double bonds.

Flashcard 19: How does bond strength relate to bond enthalpy?

Answer: Stronger bonds have higher bond enthalpies. Higher enthalpy means more energy needed to break the bond.

Flashcard 20: Calculate the bond enthalpy change for breaking 1 O=O and forming 2 O-H bonds. Use 498 and 463 kJ/mol.

Answer: $\Delta H = 498 - 2(463) = -428 \text{ kJ/mol}$. Breaking uses 498 kJ/mol, forming releases 926 kJ/mol.

Flashcard 21: Which bond is generally stronger, N≡N or N=N?

Answer: N≡N. Triple bonds have higher bond enthalpies than double bonds.

Flashcard 22: Identify whether a reaction is endothermic or exothermic when $\Delta H$ is positive.

Answer: Endothermic. Positive $\Delta H$ means energy is absorbed from surroundings.

Flashcard 23: State whether forming a bond is endothermic or exothermic.

Answer: Exothermic. Energy is released when atoms come together to form bonds.

Flashcard 24: What type of reaction is indicated if the total bond enthalpies of products are greater than reactants?

Answer: Endothermic reaction. More energy required to break bonds than released forming them.

Flashcard 25: What is the bond enthalpy of a C-H bond in kJ/mol?

Answer: Approximately 413 kJ/mol. Common value for single C-H bonds in organic molecules.

Flashcard 26: Calculate the bond enthalpy change for breaking N≡N and forming 2 N-H bonds. Use 941 and 391 kJ/mol.

Answer: $\Delta H = 941 - 2(391) = 159 \text{ kJ/mol}$. Breaking uses 941 kJ/mol, forming releases 782 kJ/mol.

Flashcard 27: What factor primarily affects the bond enthalpy?

Answer: Bond strength. Bond enthalpy reflects the energy needed to break bonds.

Flashcard 28: What is the bond enthalpy of an O=O bond?

Answer: 498 kJ/mol. Strong double bond between oxygen atoms in $O_2$.

Flashcard 29: Which bond typically has a higher bond enthalpy: C=C or C-C?

Answer: C=C. Double bonds are stronger than single bonds.

Flashcard 30: What is the definition of bond enthalpy?

Answer: The energy required to break one mole of a bond in gaseous molecules. Always measured for gaseous species at standard conditions.