Chemistry AS DF CI 4.1 and 4.3
- Created by: A.B.
- Created on: 30-11-13 10:49
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- DF Enthalpy and Entropy CI 4.1 and 4.3
- Enthalpy
- An exothermic reaction gives out energy from the system to the surroundings.The temperature of the surroundings increases.
- delta H is negative
- Endothermic opposite
- Standard enthalpy change of combustion
- Enthalpy change when 1 mole of a substance burns completely in oxygen under standard conditions.
- Standard enthalpy change of formation
- Enthalpy change when 1 mole of a substance is formed from its constituent elements. Both the reactants and products are in their standard state.
- Other reactions
- Measuring delta H in laboratory
- An exothermic reaction gives out energy from the system to the surroundings.The temperature of the surroundings increases.
- Entropy
- Measure of the number of ways in which particles can be arranged.
- Gases have a greater entropy than liquids, liquids have a greater entropy than solids.
- Mixtures (e.g. in solutions) have a greater entropy than the unmixed constituents.
- If the number of particles increases during the course of the reaction then entropy usually increases.
- Enthalpy
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