5.2.2 - Enthalpy and entropy Flashcards
Define entropy
A measure of the dispersal of energy in a system which is greater when the system is more disordered
What is the symbol of entropy?
S
Solid or gas, which is more disordered?
Gas
What is the unit of standard entropy?
J K^-1 mol^-1
How does temperature affect entropy?
The greater temperature particles have more energy and move more. Thus the arrangement of particles become more random.
More random arrangement = higher entropy
When a solid ionic lattice is dissolved in solution what happens to entropy?
Entropy increases because the ions are more disordered
How does change in number of gas molecules in a reaction affect entropy?
Increase in number of gas molecules = increase in entropy
decrease in number of gas molecules = decrease in entropy
What is equation used to calculate entropy change?
ΔS(reaction) = ΔS(products) - ΔS(reactants)
What is the Gibbs’ free energy equation?
ΔG = ΔH - TΔS
ΔG - Gibbs free energy
ΔH - Enthalpy change
T - Temp in kelvin
ΔS - Entropy change
For a reaction to occur spontaneously ΔG must be positive or negative?
Negative
What are the limitations of the predictions of feasibility made using ΔG?
- Reactions may have high activation energy
- Rate of reaction may be very slow
