CHEMICAL EQUILIBRIA Flashcards
What does the activity of a compound tell us?
The activity of a compound tells us how the free energy/chemical potential of a compoud varies with the progress of the rxn
What is the activity of a gas?
P° = standard pressure of 1 atm
What is the activity of a pure solid or liquid?
What is the activity of a solution?
C° = standard concentration of 1 M
What species are used in a mass action expression?
Gaseous and aqueous species only
What is the formula for mass action expression?
Q = products / reactants = K (when dG = 0)
What is Q?
Q is the reaction quotient, a current or “right now” condition and can be calculated at any point
What is K?
Q converges into the equilibrium constant (K) as the system reacts and adjusts
The equilibrium constant (K) is constant unless what changes?
Temperature
What does it mean when K > 1?
K > 1 ; product favored (rxn moves forward)
What does it mean when K < 1?
K < 1 ; reactant favored (rxn moves in reverse)
How is K manipulated?
- When the rxn is reversed, K becomes 1/K
- Whe the rxn is doubled, K becomes K^2
What does it mean when Q < K?
Q < K ; too many reactants, so the rxn tends to move forwards
What does it mean when Q = K?
Q = K ; the rxn is at equilibrium (dG = 0)
What does it mean when Q > K?
Q > K ; there are too many products, so the rxn tends to move in reverse
What does the plot of Gibbs free energy look like when dG° rxn < 0
What does the plot of Gibbs free energy look like when dG° rxn > 0
At what points on both these plots is the rxn reactant heavy?
Q < K at points 1 and 3
At what points on both these plots is the rxn product heavy?
Q > K at points 3 and 3
What is the formula for dG rxn?
What is the formula for dG° rxn?
What is K when dG is < 0?
K > 1 ; products are favored
What is K when dG is > 0?
K < 1 ; reactants are favored
What is Le Chatelier’s Principle?
Le Chatelier’s Principle states that when a chemical system at equilibrium experiences a change, the equilibrium shifts to counteract the imposed change and a new equilibrium established
What happens when reactants are added to a reaction?
When reactants are added, the rxn shifts to the product side
What does adding reactants result in?
Q < K
What happens when products are added?
When products are added, the rxn shifts towards the reactants
What does adding products result in?
Q > K
What happens when reactants are removed?
When reactants are removed, the rxn shifts to the reactant side
What happens when products are removed?
When products are removed, the rxn shifts to the product side
What happens when volume increases?
Increase in volume = decrease in pressure = shifts to side with greater gaseous moles
What happen when the volume decreases?
Decrease in volume = increase in pressure = shifts to side with least gaseous moles
What happens when an inert gas is added at constant pressure?
Volume increases
What happens when an inert gas is added at constant volume?
Pressure increases, however, there is no effect
What happens when temperature is added to an endothermic reaction?
Increase in temperature for an endothermic rxn (heat is reactant) = shifts to products = K increases
What happens when temperature is added to an exothermic reaction?
Increase in temperature for an exothermic rxn (heat is product) = shifts to reactants = K decreases
What is the Van’t Hoff Equation?
What is the formula for Kp?
Kp = Kc (RT) ^ dn
