equillibria Flashcards
what do all reversible reactions reach
all reversible reactions reach a dynamic equilibrium state
what are the two features of a dynamic equilibrium
- the forward reaction and backward reactions are occurring at equal rates
- the concentrations of reactants and products stay constant
what does Le Chatelier’s principle state
if an external condition is changed the equilibrium shift to oppose the change (and try and reverse it)
what effect does temperature have on equilibria
if temperature increases the equilibria will shift to oppose this and move in the endothermic direction to try to reduce the temperature by absorbing the heat
temperature is decreased the equilibrium will shift to oppose this and move in the exothermic direction to try to increase the temperature by giving out heat
what effect does pressure have on equilibria
increasing pressure will cause the equilibrium to shift towards the side with fewer moles of has to oppose the change and thereby reduce the pressure
decreasing pressure will cause the equilibrium to shift towards the side with more moles of has to oppose the change and thereby increase the pressure
if the number of moles is the same on both sides of the equation then changing pressure will have no effect on the position of the equilibrium
why do industries favour high pressures
increasing pressure may give a higher yield of product and will produce a faster rate
Industrially high pressure is expensive to produce (high electrical energy cost for pumping the gases to make a high pressure) and the equipment (to contain the high pressures)
what effect if catalyst on equilibrium
a catalyst has no effect on the position of equilibrium, but it will speed up the rate at which the equilibrium is achieved
it does not affect the position equilibrium because it speeds up the rates of the forward and backward reactions by the same amount
how can we improve the overall yield of an industry reaction
recycling unreacted reactants back into the reactor can improve the overall yield of the process in the industry
what does the effect of changing conditions have on the value of Kc
Kc is equilibrium constant
the larger the Kc the greater the number of products
If Kc is small er say the equilibrium favours the reactants
what changes Kc
it does not change if pressure or concentration is altered
A catalyst also has no effect on Kc
both the position and the value of Kc will change it temperature is altered
if fewer products are formed then the value of Kc decreases
how does pressure change Kc
the position of equilibrium will change it pressure is altered but the value of Kc stays constant as Kc only varies with temperature
why does the value of Kc not change with a catalyst
catalysts have no effect on the value of Kc or the position of equilibrium as they speed up both forward and backward rates by the same amount
