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: 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 2: 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 3: 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 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: 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 6: What is the bond enthalpy of a N=N bond?

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

Flashcard 7: What is the bond enthalpy of a H-Cl bond?

Answer: 431 kJ/mol. Standard value for hydrogen-chlorine bonds in HCl.

Flashcard 8: 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 9: 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 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-H bond in kJ/mol?

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

Flashcard 12: What is the bond enthalpy of a C-O bond in methanol?

Answer: 358 kJ/mol. Standard value for carbon-oxygen single bonds.

Flashcard 13: State whether breaking a bond is endothermic or exothermic.

Answer: Endothermic. Energy is required to overcome attractive forces between atoms.

Flashcard 14: Which bond typically has a higher bond enthalpy: C=C or C-C?

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

Flashcard 15: 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 16: 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 17: What is the bond enthalpy of an O=O bond?

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

Flashcard 18: 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 19: What is the bond enthalpy of a C≡C bond?

Answer: 839 kJ/mol. Standard value for carbon-carbon triple bonds.

Flashcard 20: What is the bond enthalpy of an O=O bond?

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

Flashcard 21: What is the bond enthalpy of an F-F bond?

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

Flashcard 22: 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 23: 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 24: State whether forming a bond is endothermic or exothermic.

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

Flashcard 25: 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 26: Which bond is generally stronger, N≡N or N=N?

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

Flashcard 27: State the formula for calculating the change in enthalpy using bond enthalpies.

Answer: $\Delta H = \sum \text{(bond enthalpies of bonds broken)} - \sum \text{(bond enthalpies of bonds formed)}$. Energy in minus energy out gives the net enthalpy change.

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

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

Flashcard 29: Identify the unit commonly used for bond enthalpy.

Answer: Kilojoules per mole (kJ/mol). Standard unit for expressing energy per mole of substance.

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.

Flashcard 31: What is the bond enthalpy of a N=N bond?

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

Flashcard 32: 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 33: State whether forming a bond is endothermic or exothermic.

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

Flashcard 34: 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 35: State whether breaking a bond is endothermic or exothermic.

Answer: Endothermic. Energy is required to overcome attractive forces between atoms.

Flashcard 36: State whether breaking a bond is endothermic or exothermic.

Answer: Endothermic. Energy is required to overcome attractive forces between atoms.

Flashcard 37: What factor primarily affects the bond enthalpy?

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

Flashcard 38: What is the bond enthalpy of a C-C bond?

Answer: 348 kJ/mol. Standard value for single carbon-carbon bonds.

Flashcard 39: What is the bond enthalpy of an N-H bond?

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

Flashcard 40: 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 41: What is the bond enthalpy of a C≡C bond?

Answer: 839 kJ/mol. Standard value for carbon-carbon triple bonds.

Flashcard 42: What is the bond enthalpy of a C-Cl bond?

Answer: 328 kJ/mol. Standard value for carbon-chlorine single bonds.

Flashcard 43: 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 44: What factor primarily affects the bond enthalpy?

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

Flashcard 45: What is the bond enthalpy of an F-F bond?

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

Flashcard 46: 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 47: 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 48: What is the bond enthalpy of a C-N bond?

Answer: 305 kJ/mol. Standard value for carbon-nitrogen single bonds.

Flashcard 49: Which has a higher bond enthalpy: a single bond or a triple bond?

Answer: A triple bond. More bonds mean stronger attraction and higher enthalpy.

Flashcard 50: What factor primarily affects the bond enthalpy?

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

Flashcard 51: What is the bond enthalpy of an N-H bond?

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

Flashcard 52: Which bond typically has a higher bond enthalpy: C=C or C-C?

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

Flashcard 53: What is the bond enthalpy of an O=O bond?

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

Flashcard 54: 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 55: 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 56: Calculate the bond enthalpy change: breaking 1 C-C and forming 2 C-H. Use 348 and 413 kJ/mol.

Answer: $\Delta H = 348 - 2(413) = -478 \text{ kJ/mol}$. Breaking uses 348 kJ/mol, forming releases 826 kJ/mol.

Flashcard 57: 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 58: 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 59: Calculate the bond enthalpy change for breaking 2 C=C and forming 3 C-C. Use 614 and 348 kJ/mol.

Answer: $\Delta H = 2(614) - 3(348) = 240 \text{ kJ/mol}$. Breaking uses 1228 kJ/mol, forming releases 1044 kJ/mol.

Flashcard 60: 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 61: 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 62: Which bond is generally stronger, N≡N or N=N?

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

Flashcard 63: What is the bond enthalpy of a N=N bond?

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

Flashcard 64: State whether forming a bond is endothermic or exothermic.

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

Flashcard 65: 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 66: 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 67: What is the bond enthalpy of an N-H bond?

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

Flashcard 68: Which bond is generally stronger, N≡N or N=N?

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

Flashcard 69: 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 70: What does a negative enthalpy change indicate about a reaction?

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

Flashcard 71: What happens to bond enthalpy as bond length increases?

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

Flashcard 72: 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 73: What happens to bond enthalpy as bond length increases?

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

Flashcard 74: 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 75: 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 76: Identify the bond with the lowest bond enthalpy: H-H, Cl-Cl, F-F.

Answer: F-F. Lone pair repulsion makes F-F weakest among halogens.

Flashcard 77: 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 78: What is the bond enthalpy of a C-F bond?

Answer: 485 kJ/mol. Strong bond due to high electronegativity of fluorine.

Flashcard 79: What is the bond enthalpy of a C-F bond?

Answer: 485 kJ/mol. Strong bond due to high electronegativity of fluorine.

Flashcard 80: Which bond typically has a higher bond enthalpy: C=C or C-C?

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

Flashcard 81: 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.