Practice question · Match the pairs
Match each thermochemical quantity to its definition.
- Standard enthalpy of formation
- Standard enthalpy of combustion
- Bond dissociation enthalpy
- Lattice enthalpy
- Breaking one mole of a bond in the gas phase
- Forming one mole of a compound from its elements
- Separating one mole of an ionic solid into gaseous ions
- Burning one mole completely in excess oxygen
Hints
- Each is defined per mole of a specific change.
- One concerns making a compound, one destroying it by burning, and two concern breaking things apart.
Show the answer
- Standard enthalpy of formation → Forming one mole of a compound from its elements
- Standard enthalpy of combustion → Burning one mole completely in excess oxygen
- Bond dissociation enthalpy → Breaking one mole of a bond in the gas phase
- Lattice enthalpy → Separating one mole of an ionic solid into gaseous ions
Why
Each standard enthalpy fixes both the amount (one mole) and the exact process, so that values from different laboratories can be added in a Hess cycle without ambiguity.
Practise Enthalpy and Thermochemistry
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