Equilibria and rates Flashcards
What is the equation for ΔG?
ΔG = - RTlnKeq
What happens if ΔG is negative?
The reaction is exothermic, and equilibrium favours the products
What happens if ΔG is positive?
The reaction is endothermic and equilibrium favours the reactants
What happens if ΔG is zero?
Reactants and products have the same energy and Keq = 1
What happens when there are small changes in ΔG?
Big differences in Keq
What happens to the % of the more stable state at equilibrium as ΔG decreases?
Increases
When ΔG is large and negative, causing Keq to be large, what does the reaction become?
Effectively irreversible
How would you drive equilibria to one side in the formation of an ester?
Remove the water as it forms as the amount of ester will increase to keep the concentrations the same
What are the components of ΔG?
ΔG = ΔH - TΔS
What is ΔH?
Enthalpy change
mostly due to changes in bond strength
What is ΔS?
Entropy
Amount of disorder in a system
What is an unfavourable entropy change?
From 2 molecules to one molecules
As this decreases disorder and molecules like disorder
What is an unfavourable enthalpy change?
if the bonds you form have a smaller energy than the bonds youve broken
eg. C=O > 2 x C - O
What determines the rate of reaction?
the activation barrier
What is the arrhenius equation?
K = Ae ^ -Ea/RT
What do small changes in Ea cause?
Big differences to K
What is the kinetic product?
The one that forms the fastest
What ΔG does the kinetic product have in comparison to the thermodynamic product?
Lower ΔG
What types of reactions are under kinetic control?
Irreversible
What is the thermodynamic product?
Most stable with the lower energy
What types of reactions are under thermodynamic control?
Reversible
Why are low temperatures used in reactions?
To prevent unwanted reactions
