3.2.3 Chemical Equilibrium Flashcards
what is dynamic equilibrium
when forwards and backwards reactions are occurring at the same rate
conc of reactants and products stays the same and the reaction is continuous
what does Le Chatelier’s principle state
if an external condition is changed then the equilibrium will shift to oppose the change
effect of increasing temperature on equilibrium
shift to oppose the change
favour the endothermic reaction
to try and reduce the temperature by absorbing heat
effect of decreasing temperature on equilibrium
shift to oppose the change
favour the exothermic reaction
to try and increase the temperature by giving out heat
what effect would increasing the temperature have on the yield of ammonia
N2 + 3H2 (reversible) 2NH3
if temp increased the equilibrium will shift to oppose this and move in the endothermic backwards direction to try and decrease the temperature
position of equilibrium will shift towards the left
yield of ammonia reduced
effect of pressure on equilibrium
increasing pressure cause the equilibrium to shift towards the side with fewer moles of gas to oppose the change and reduce the pressure
when does pressure have no effect on the rate of reaction
if the number of moles of gas on each side of the reaction are the same
advantages and disadvantages of increasing pressure
+ may give a higher yield of product
+ faster rate
-high electrical energy costs for pumping gases to make them high pressure
-equipment to contain gases at high pressure is expensive
effect of concentrations on equilibrium
increase left then eqm will shift to oppose and try to remove the product just formed
effect of catalysts on equilibrium
no effect on the position
will speed up both equations equally to speed the rate that equilibrium is reached
equilibrium processes
haber process
contact process
production of methanol form CO
hydration of ethene to produce ethanol
haber process
N2 + 3H2 (reversible) 2NH3 exothermic
T=450 P= 200-1000 atm
iron catalyst
low temp= good yield and slow rate, compromise
high pressure= good yield and high rate, not higher due to costs
contact process
stage 1: S (s) + O2 (g) -> SO2 (g)
stage 2: SO2 (g) + 1/2 O2 (g) (reversible) SO3 exothermic
T=450 P= 1-2 atm
catalyst= V2O5
low temp= good yield but slow rate, compromise
high pressure= slightly better yield and high rate, not too high due to costs
production of methanol from CO
CO (g) + 2H2 (g) (reversible) CH3OH (g) exothermic
T=400 P=50
catalyst= chromium and zinc oxides
low temp= good yield but slow rate, compromise
high pressure= good yield and high rate, not too high due to costs
hydration of ethene to produce ethanol
CH2=CH2 (g) + H2O (g) (reversible) CH3CH2OH exothermic
T=300 P=70 catalyst= conc H3PO4
low temp= good yield slow rate, compromise
high pressure= good yield and high rate, not too high as leads to unwanted polymerisation of ethene toi polyethene
