A2- Entropy Flashcards
What is entropy?
measure of disorder of a system
What are the units for entropy?
J K^-1 Mol^-1
What is the equation for entropy change?
(change in)S = Sproducts - Sreactants
What is the equation for free energy?
(change in)G = (change in)H - T(change in)S
Why do substances tend more towards disorder?
as they are require less energy do are more energetically stable
Describe the feasibility where enthalpy change and entropy change are both -ve
always feasible
Describe the feasibility where enthalpy change and entropy change are both +ve
feasible at higher temperatures
Describe the feasibility where enthalpy change is +ve and entropy change is -ve
never possible
Describe the feasibility where enthalpy change is -ve and entropy change is +ve
feasible at lower temperatures
What must the value of G be for a reaction to be feasible/spontaneous?
0 or below
what is the formula to determine the temperature where a reaction becomes feasible/spontaneous?
T = (change in)H / (change in)S
What can affect entropy change?
- number of moles
- state
Why can some enthalpically unstable reactions still be spontaneous/feasible?
as they are entropically favourable
Why might some feasible reactions not occur?
activation energy is too high
How do you calculate enthalpy change?
(sum H products) - (sum H reactants)
