Chemical Equilibrium Flashcards
In what type of system can a chemical equilibrium occur and why?
A chemical equilibrium can only occur in a closed system as only energy is exchanged with the surroundings and not matter allowing for a constant to be reached.
What is a reversible reaction?
A reaction that can go in either the forward or reverse direction.
Explain a dynamic equilibrium
At dynamic equilibrium both reactants and products are present, macroscopic properties are constant (concentrations of reactions and products) and the rate of the forward reaction is equal to the reverse reaction.
Explain physical equilibrium
Equilibrium involving a change in state, e.g. Ice to water
What is the Haber process?
The Haber process combines nitrogen from the air with hydrogen derived mainly from natural gas (methane) into ammonia which is a reversible reaction.
What is Le Chatelier’s Principle
If a closed system at equilibrium is disturbed then the system adjusts itself so as to minimise the disturbance.
What factors affect equilibrium?
Temperature
Concentration
Pressure (gasses)
Catalyst
How does temperature affect equilibrium?
In an exothermic reaction, increased temperature moves the graph to favour the reactants (reactant conc. will increase) and vise versa.
How does concentration affect equilibrium?
Increasing the concentration of a reactant will shift the equilibrium to the right and cause increased concentration of the product, and decreased reactants.
How does gas pressure affect equilibrium?
As total gas pressure is increased the equilibrium moves to the direction that tends to reduce pressure. It shifts to the side with the least moles.
How do catalysts affect equilibrium?
A catalyst will lower the activation energy of both the forward and reverse reaction by the same amount, increasing the rate at which equilibrium in increased.
What is Kc and its equation
Kc is the equilibrium law expression taken at equilibrium and shows the proportion of reactants and products.
If Kc>1, products are favoured
If Kc<1, reactants are favoured
Kc can only be changed by temperature
Kc=((Products)^coefficient)/((reactants)^coefficient)
What is the reaction quotient?
The reaction quotient (Qc) is used to find the relative amounts of products and reactants in a reaction at any given time.
The formula is the same as Kc.
If:
Qc>Kc, equilibrium shifts left
Qc=Kc, equilibrium stays the same
Qc<Kc, equilibrium shifts right
