Enthalpy of Formation
Definition
The enthalpy change that occurs when one mole of a compound is formed from its constituent elements in their standard states.
Analogy
Imagine you're building a Lego castle. The energy it takes to put together all the individual Lego pieces into the final castle structure can be thought of as the enthalpy of formation.
Related terms
Heat of Reaction: The total amount of heat absorbed or released during a chemical reaction.
Bond Energy: The amount of energy required to break one mole of a bond in a substance to separate atoms in gas phase.
Hess's Law: A law stating that the total enthalpy change for a reaction is independent of the pathway, i.e., it depends only on the initial and final states.
"Enthalpy of Formation" appears in:
Study guides (3)
Practice Questions (12)
- What is the enthalpy of formation of ethene (C2H4) given the following bond energies? C-C = 348 kJ/mol; C=C = 612 kJ/mol; C-H = 413 kJ/mol.
- Which of the following statements regarding enthalpy of formation is true?
- What is the standard state for enthalpy of formation calculations?
- The enthalpy of formation of which of the following is zero?
- Which of the following statements regarding enthalpy of formation is true?
- What is the enthalpy of formation of water (H2O) given the following bond energies? O=O = 498 kJ/mol; O-H = 463 kJ/mol; H-H = 436 kJ/mol.
- What is the standard enthalpy of formation of C6H6(g) given the bond enthalpies: C-C = 347 kJ/mol; C=C = 611 kJ/mol; H-H = 436 kJ/mol; C-H = 413 kJ/mol?
- What is the standard enthalpy of formation of CaSO4(s) given the bond enthalpies: Ca-O = 494 kJ/mol; S-O = 523 kJ/mol?
- If the bond enthalpy of O-H is 467 kJ/mol and the bond enthalpy of O=O is 495 kJ/mol, what is the enthalpy of formation of water?
- Given the bond enthalpies: O=O (495 kJ/mol); H-H (436 kJ/mol); and O-H (467 kJ/mol); what is the enthalpy of formation of water?
- Which of the following statements regarding enthalpy of formation is false?
- What is the enthalpy of formation of methane (CH4) given the following bond energies? C-C = 348 kJ/mol, C-H = 413 kJ/mol, H-H = 436 kJ/mol.
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