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DYNAMIC EQUILIBRIUM
Reversible reactions go both ways. You use a sign.
H2 + I2 2HI
This reaction goes in either direction.
2HI H2 + I2
As the reactants get used up, the forward reaction
slows down; more product formed. Reverse speeds
up.
"When the forward reaction is the same rate as the
backward" dynamic equilibrium occurs. This is only
possible in a closed system ie; nothing can get in or
out!…read more

Slide 3

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LE CHATELIER'S PRINCIPLE
Predicts what's going to happen if the conditions
change.
If the concentration, pressure or temperature are
changed in a reaction, the position of the
equilibrium changes. So we get different
amounts of reactants and products!
Shifts to the left: Shifts to the right:
H2 + I2 2HI H + I 2HI
2 2
MORE REACTANTS MORE PRODUCTS
"when a change is applied to system in dynamic
equilibrium, the systems acts in a way to counteract the
change"
So: raising the temperature causes the equilibrium to shift
to cool it down!…read more

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HANDY RULES FOR LE CHATELIER'S..
CONCENTRATION:
2SO2 + O2 2SO3
If you increase the concentration of reactants, the equilibrium tries to
get rid by making more products, so.. the equilibrium's shifted to
the right! Increasing the conc' of products moves the equilibrium to
the left to remove the extra. Decreasing concentrations has the
opposite effect.
PRESSURE:
2SO2 + O2 2SO3
Only affects equilibria with gases. Increases in pressure moves
equilibrium to the side with fewer molecules to reduce pressure.
Decreasing pressure shifts equilibrium to side with more molecules
to raise pressure.
TEMPERATURE:
2SO2 + O2 2SO3 H= -197 kjmol-1
Increase in temperature adds heat. Equilibrium moves endothermic
way(positive H). Decreasing removes heat so it shifts in exothermic
direction(negative H) . If the forward reaction is endothermic, the…read more

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CATALYSTS
THEY HAVE NO AFFECT THE
POSITION OF THE
EQUILIBRIUM!
They can't increase yield but..
Do increase the speed of reaction..
By lowering the activation energy (energy
needed to kick start the reaction)..
Meaning equilibrium is reached faster!…read more

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ETHANOL
Can be formed from ETHENE and STEAM.
The industrial production of ethanol is an
example of Le Chatelier's in real life..
Ethanol is produced via a reversible
exothermic reaction between ethene and
steam.
C2H4 + H2O C2H5OH H= -46 kjmol-1
The reaction's done at pressures of 60-70
atmospheres and temperatures of 300 ° C…read more

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