Equillibrium

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Reversible Reactions
If a reversible reaction takes place inside a closed system
e.g. bottle with cork in it it will reach a dynamic
equilibrium. This happens as the closed system prevents
any products escaping and so the forward reaction happens
at exactly the same rate as the reverse reaction so the
overall effect of the reactions is nil as as the forward and
reverse reactions can cancel out. Remember that the
reactions are still going on just at the same rate in opposite
directions which causes them to have no effect ­ this is why
it Is said to reach a dynamic equilibrium as dynamic means
moving or changes which reminds you that the reaction is
still going on.
What can affect an equilibrium?
Temperature
If the forward reaction is exothermic and the temperature
increases then the yield of product decreases.
If the forward reaction is exothermic and the temperature
decreases the yield of the product increases.
If the forward reaction is endothermic and the temperature
increases the yield of the product increase
If the forward reaction is endothermic and the temperature
decreases the yield of the product also decreases
Pressure
The pressure always favours the reaction with the fewest
molecules.
If there are fewer molecules on the right (products are)
then the yield of the product increases and the rate of
reaction increases
If there are fewer molecules on the left (reactants are) then
the yield of the product decreases ad the rate of reaction
decreases
If there are equal molecules on both sides then it will have
no effect on the rate of reaction.

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Catalysts do not affect the position of the equilibrium.
The higher the pressure the higher the concentration which
increases the rate of reactions as it increases the number of
successful collisions.…read more

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