Chapter 4: Energetics/Thermochemistry
Energetics, or thermochemistry, focuses on the energy changes during chemical and physical processes, especially the enthalpy changes involved. Understanding exothermic and endothermic reactions is crucial, along with techniques like calorimetry and Hess's Law for calculating enthalpy changes. Bond enthalpies provide a method for estimating reaction energy changes, while Gibbs free energy integrates enthalpy and entropy to predict reaction spontaneity.
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What we have learnt
- Energetics is the study of energy changes during chemical and physical processes.
- Enthalpy changes can be measured using calorimetry and are essential for understanding heat transfer in reactions.
- Gibbs free energy combines enthalpy and entropy to determine the spontaneity of a reaction.
Key Concepts
- -- Enthalpy (H)
- A thermodynamic property representing the total heat content of a system at constant pressure.
- -- Exothermic Reaction
- A reaction that releases heat to the surroundings, resulting in a negative enthalpy change (ΔH < 0).
- -- Endothermic Reaction
- A reaction that absorbs heat from the surroundings, resulting in a positive enthalpy change (ΔH > 0).
- -- Hess's Law
- States that the overall enthalpy change of a reaction is equal to the sum of the enthalpy changes for each individual step.
- -- Bond Enthalpy
- The energy required to break one mole of a specific type of bond in the gaseous state.
- -- Gibbs Free Energy (G)
- A thermodynamic potential that measures the 'useful' work obtainable from a thermodynamic system, integrating enthalpy and entropy.
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