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Energetics (Gibbs energy ΔG (Exothermic (TΔS>ΔH
TΔS = +ve -ΔG …
Energetics
Gibbs energy ΔG
ΔG= ΔH- TΔS, where T is the temperature in Kelvin
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Entropy change ΔS
Factors affecting
Change in state
- Solids have low entropy because atoms vibrate at their fixed positions. There is a limited number of ways to arrange the atoms and distribute the energy between atoms
- Liquids have a higher entropy than solid because atoms are sliding past one another, free to move in the container. There are more ways to arrange the atoms and to distribute energy between these particles
- Gas has the highest entropy because the atoms are far apart from one another and their motion is highly chaotic. Larger volume allows even more ways to arrange the atoms and molecules and distribute energy between the gaseous particles
Change in temperature
- Temperature increases means that KE increases. This causes the broadening of the Maxwell-Boltzmann energy distribution which results in more ways of arranging the energy quanta in the hotter system ΔS>0
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Mixing of particles
- Gas always mix completely to create a more disordered system
To check for ΔS
- Compare stoichiometry of reactants and products in a balanced equation
If n(reactants) > n(products), decrease in disorder = -ΔS
- Compare physical state of the reactants and products
S(gas)>S(liquid)>S(solid)