UNIT 7 - Equilibrium Flashcards
State the equation for determining the equilibrium constant through its free energy change.
delta G= -RT ln Kc
State the effect of a change on temperature on the equilibrium position and Kc.
increase in T = increase in the value of Kc for endothermic and a decrease for an exothermic reaction
exothermic - decrease in T -> producing heat and thus favouring the forward reaction (equilibrium to the right)
exo - increase in T will favour the backward endothermic reaction
endo - decrease in T -> favour backward exothermic reaction
endo - increase in T -> favour forward endothermic reaction
State the meaning of Kc value.
Kc > 1 - very high conversion of reactants into products (equilibrium lies to the right)
Kc < 1 - reaction hardly proceeds (equilibrium lies to the left)
State the Le Chatelier’s principle.
A system at equilibrium when subjected to a change will respond in such a way as to minimize the effect of the change.
State the effect of a change on pressure on the equilibrium position and Kc.
Kc - remains unchanged
depends on the relative number of gas molecules
increase in pressure favors the side of an equilibrium reaction that has the smaller number of gas.
State the relationship between the equilibrium constant and the specific reaction.
Fixed for a particular reaction at a specified temperature.
Define equilibrium state.
The reaction takes place at the same rate as its reverse reaction.
No net change is observed.
State and explain the features of equilibrium state.
- dynamic - reaction has not stopped but both forward and backward reactions are still occurring at the same rate.
- achieved in a closed system - no exchange of matter with the surroundings.
- concentrations of reactants and products remain constant - are being produced and destroyed at an equal rate.
- no change in macroscopic properties - observable properties (colour, density) depend on the concentrations of components of the mixture.
- can be reached in either direction - same equilibrium mixture will result under the same condition.
How will the system at equilibrium respond to a change.
So as to minimize the effect of the change.
State the relationship between the equilibrium and the Gibbs free energy.
Equilibrium will occur when a reaction mixture is at the minimum value of the Gibbs free energy.
delta G < 0 - reaction proceeds in the forward direction
delta G>0 - reaction proceeds in the backward direction
delta G = 0 - reaction is at equilibrium
Define the equilibrium constant.
Ratio of the rate constants of the forward and backward reaction.
Kc = k/k’
State the equilibrium constant expression.
Kc= ([C] ^c [D]^d) / ([A]^a [B]^b)
for
aA + bB -> cC + dD
FOR HOMOGENOUS REACTIONS (in the same state)
Describe the delta H relation to equilibrium.
Its usually given for the forward reaction and so if
its negative sign ->
forward reaction - exothermic
backward - endothermic
What does the magnitude of equilibrium constant give information about.
How far a reaction goes at a particular temperature.
NOT about how fast it will achieve the equilibrium state.
Define the equilibrium position.
Proportion of reactant and product in the equilibrium mixture.
