Unit 3 Flashcards
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
Q>K
too many products and shifts left to reach equilibrium
reaction will shift to reach K
Q
too many reactants
shifts right to reach equilibrium
Q=K
at equilibrium
ICE tables
initial
change
equilibrium
table can be made using moles, concentrations, pressures