Equilibria
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what does the term dynamic mean
both forward and backward reactions are occurring simultaneously
what are two features of dynamic equilibrium
• Forward and backward reactions are occurring at equal rates. • The concentrations of reactants and products stay constant
will a reaction go to completion in an open or closed system
an open system
what are the conditions for equilibrium
• it can only be achieved in a closed system • it can be approached from either direction and the final position of equilibrium will be the same • it is a dynamic process • when equilibrium is reached, the macroscopic properties of the system do not change with time
what is Le Chatelier’s Principle
a system at equilibria will act to oppose any changes in conditions
what are two ways to shift equilibria to the right in terms of concentration
• increase concentration of reactants (add more) • reduce the concentration of the products
what are two ways to shift equilibria to the left in terms of concentration
• increase the concentration of the products (add more product) • decrease the concentration of the reactants (remove some reactants)
when would pressure effect equlibrium (2)
• when it only involves gases • when there are a different number of moles on either side
if you were to increase the pressure which way would equilibrium shift
increasing the pressure would shift equilibrium to the side with less moles
if you were to decrease the pressure which way would equilibrium shift
decreasing the pressure would shift the equilibrium to the side with more moles
if you were to increase the temperature which way would equilibrium shift
increasing the temperature, shifts equilibrium to the endothermic reaction to oppose the increase in temp
if you were to decrease the temperature which way would equilibrium shift
decreasing the temperature, shifts equilibrium to the exothermic reaction to oppose the decrease in temp
what effect do catalysts have on the position of equilibrium
they have no effect • as they alter the forwards and backwards reactions equally
why are catalysts important for industry
as they allow equilibrium to be reached quicker
what do you need to consider when using equilibrium in industry
yield, cost and time
what would the IDEAL conditions be for the production of ammonia, then what is the compromise
• use a low temperature (slow rate) and high pressure (too high energy costs) • comprimised with 670K and 2000KPa with an iron catalyst
what happens to ammonia after it is produced
• it is cooled, condensed and piped off • unreacted nitrogen and hydrogen are separated and fed back into the reactor
what is the equation for the industrial production of ethanol
ethene + water –> ethanol (all gas)
how is the reaction for ethanol sped up
by a catalyst of phosphoric acid absorbed on silica
what is the IDEAL conditions for the production of ethanol for maximum yield and practical problems
• high pressure (high energy costs)(unwanted polmeristation) • low temperature (slow rate) • excess steam ( too much dilutes the catalyst)
what is the compromise for the production of ethanol
• temp - 570K • pressure - 6700KPa • unreacted ethene is separated from the reaction mixture and recycled over the catalyst until a total conversion of 95% is achieved
what is the production of ethanol called
hydration of ethene
what is the equation for making methanol
• CO (g) + 2H2(g) ⇌ CH3OH (g) • H = -ve exo
what are the IDEAL conditions for the production of methanol but what are the practical problems
• low temperature (slow rate) • High pressure (high energy costs)(unwanted polymerisation of ethene)