Chemical Equilibrium Flashcards
Chemical Equilibrium
A state in which the rates of the forward and reverse reactions are equal and the concentrations of the reactants and products remain constant.
What condition must be met to establish equilibrium (rats, cats, tats)
-reversible reaction
-closed system
-temperature must remain the same
Explain why equilibrium is dynamic
Both forward and reverse reactions take place but their rates are equal so there are no measurable changes in concentrations of reactants or products.
What does Keq represent
The mathematical ratio which represents the proportion of products to reactants
If Keq>1
the forwards reaction or products are favoured: the reaction essentially goes to completion all are or most reactants are used up to form the products.
If Keq<1
the reverse reaction or reactants are favoured: the reaction does not occur to any great extent-most of the reactants remain unchanged, and there are few products produced
Le Chatelier’s Principle
States that if a system at equilibrium is subjected to an external stress, the equilibrium will shift to minimize the effects of that stress.
Changes in concentration (chateliers)
Increase reactants- shifts to products side
Decrease reactants- shifts to reactants
When does the change of pressure or volume affect the reaction
If gases are present
Increasing pressure (reducing volume) will:
the equilibrium moving towards the side with the fewest moles of gas molecules
Decreasing pressure (increasing volume)
Shift to the side with the most moles of gas
Temperature is increases
Will shift so that the temperature is reduced again
Exothermic reaction: favours endothermic
Endothermic reaction: favours exothermic
Temperature is decreased
Will shift to side where heat was originally
Adding a catalyst
Has no effect on equilibrium will only make it reach equilibrium sooner
when temp changes equilibrium and alters the value of Keq, describe what happens to Keq
If the forwards reaction is favoured: more products therefore Keq will increase
If the reverse reaction is favoured: fewer products more reactants therefore Keq will decrease
