can you obtain 100% conversion in a reversible/equilibrium rxn
no, will always result in a mixture of reactants and products
equilibrium position
when forward rxn slows and reverse rxn speeds up until they are taking place at the same rate
- describe the concentration of reactant and product at this point (will be constant but not always equal)
where can equilibrium be achieved
- only in a closed system (rxn takes place in a seal container)
macroscopic properties to tell eq’m has been reached (l)->(g)
- liquid level will decrease at first as more particles are becoming gaseous
- eq’m reached when liquid level stops decreasing (no more change)
4 condition that apply to all equilibrium systems
- 2 opposing processes are going at an equal rate
- the system undergoes no observable changes
- can only exist in closed system
- eq’m can be achieved from either direction
dynamic equilibrium
where rates of the forward and reverse rxns are equal but the properties/concentrations are constant
- dynamic as reactions are still occuring, at same rate
what is the K value affected by
temperature
what is not included in an equilibrium constant expression
- don’t included pure solids/liquids in an equilibrium constant expression
what happens for Kc when you reverse an equation
- it becomes inverted
R–>P = K
P–>R = 1/K
when you multiply/divide each coefficient in a balanced equation, what happens to Kc
- multiply: raise Kc to corresponding power
- divide: take corresponding root of Kc
what happens to the Kc when you combine individual equations
- multiply their Kc to obtain Kc for net reaction
what does a large Kc represent
- extent of rxn
- reaction that goes almost to completion so high conc. of products
what does a small Kc represent
- extent of rxn
- reaction that is incomplete, low conc. of products
at what Kc is a rxn most likely to reach eq’m
when Kc is neither very large or very small
what does the reaction quotient represent
- can be used to determine the position of a reaction relative to the final equilibrium at any point in time
reaction quotient where there are pure reactants
0
reaction quotient when there are pure products
infinity/undefined
reaction quotient when there is 1 mol of each species
1
how can the reaction quotient determine direction of rxn
- if Q=Kc, at equilibrium
- if Q<Kc, rxn proceeds forward to eq’m (left of eq’m)
- if Q>Kc, rxn proceeds in reverse direction to eq’m (right of eq’m)
importance of LeChatelier’s principle
to predict the qualitative effects of changes of temp, pressure, and conc. on the position of equilibrium + value of eq’m constant
what is lechatelier’s principle
- a system at equilibrium when subjected to a change will respond in a way to minimize the effect of the change
(what is done to a system at equilibrium, it will respond in the opposite way, est. a new eq’m)
how does a rxn shift when a reactant is added/removed
- added: towards the products
- removed: towards reactant
how does a rxn shift when a product is removed
- shifts towards products
how does a rxn shift when pressure is increased (or volume decreased)
- shift in direction that produces the least number of molecules
