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equilibrium reaction

the concentrations of all reactants and products remain constant with time. it is highly dynamic as the reaction never stops. there is no limiting reactants


stoichiometric reaction

proceed to completion therefore the amount of limiting reactant the remains is negligible


equilibrium lies to the right

it favours the products, concentrations of reactants is never 0


equilibrium lies to the left

it favours the reactants


how can you disturb the "system"

temperature, change volume, changing something will stress the system and change the equilibrium


when is equilibrium reached

when rate of forward reaction equals the rate of reverse reaction


the equilibrium expression (K or Kc)

is a thermodynamic quantity
eqn is products to power of coefficients/reactants to power of coefficients
it has no units and concentrations are always in Mol/L
must always be accompanied by a balanced them eqn


reverse K

always needs a new equation! it is written as K^-1


when the reaction is multiplied by a factor

multiply the exponents by the factor.


equilibrium position

K is always the same for a certain temperature but the concentrations might change.
each equilibrium concentration is called the position and there is an infinite number of positions at a certain temperature


when K>1

the system will favour the products
equilibrium lies to the right
K>>10^3, reaction will essentially be products


when K<1

the system will favour the reactants
equilibrium lies to the left
K<<10^3, reaction will essentially be reactants
this would be a non-reaction but that is a lie!


equilibrium and kinetics

- size of k and time are not directly related
- time to reach equilibrium depends on the rate of reaction which is determined by kinetics
- size of K is determined by thermodynamics factors such as difference in energy between products and reactants


heterogeneous equilibrium

not all reactants are in the same state
- pure solis and liquids have concentrations that don't change and are constant so they can be ADDED to the constant equilibrium value (remove them from the eqn!)


decrease the temperature of equilibrium

that decreases the energy to be more endothermic, the equilibrium shifts right and makes the reaction more exothermic to make up for the energy lost


increase the temperature of equilibrium

that increases the energy to be more exothermic, the equilibrium shifts left and makes the reaction more endothermic to make up for the energy


increase the pressure

increase the pressure, the system respond by decreases the pressure by shifting to the side with less gas moles therefore shifting (left/right)


decrease the pressure

decrease the pressure, the system respond by increases the pressure by shifting to the side with more gas moles therefore shifting (left/right)


effect of concentration

has no effect on k,
if you increase the concentration, the system respond by decreasing the concentration of that reactant and shifting (left/right)


reaction quotient, Q

calculate the same way as K but it is used if you don't know the concentrations at equilibrium



too many products and shifts left to reach equilibrium
reaction will shift to reach K



too many reactants
shifts right to reach equilibrium



at equilibrium


ICE tables

table can be made using moles, concentrations, pressures


le chatalier's principle

if a change is imposed on a system at equilibrium, the position of the equilibrium will shift in a direction that tends to reduce that change


how to change the pressure of equilibrium

- add or remove a gaseous reactant or product (addition of an inert gas has no effect on the concentrations or partial pressures of the reactants or products) so NO CHANGE
- add another inert gas that does not react
- change the volume of the container


when you change the volume of the container

- concentrations of both reactants and products are also changed
- when volume is reduced, pressure increases and system decreases its own pressure
- it decreases the total number of gas moles in the system


by changing the temperature, you affect...

the value of K, and you treat energy as a reactant or product


adding a catalyst

does not change the equilibrium in any way, it just changes the time it takes to get to equilibrium


when a salt dissolves

ions get surrounded by water. its never entirely soluble so an equilibrium occurs