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AQA
Physical
3.1.6 Equilibria
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Created by
Paul Evangelou
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Cards (20)
All
reversible
reactions reach a
dynamic equilbrium
state
Two features of dynamic equilibrium:
Forward and backward reactions occuring at
equal
rates
Concentrations
of both reactants and products remain
constant
State Le Chatelier’s principle:
"If a system at equilibrium is
disturbed
, the equilibrium moves in the direction that tends to
reduce
the
disturbance
"
What is the effect of increasing temperature on equilibrium?
equilibrium shifts in the
endothermic
direction
tries to reduce temperature by
absorbing
heat
What is the effect of decreasing temperature on equilibrium?
equilibrium shifts in the
exothermic
direction
attempts to increase temperature by giving out heat
What is the effect of increasing pressure on equilibrium?
equilibrium
shifts to the side with fewer moles
to oppose reduce change and
reducing
pressure
What is the effect of decreasing pressure on equilibrium?
equilibrium shifts to the
side
with more moles
to oppose the change and increase
pressure
If the number of mols of gas is the same on both sides of a reversible reaction, pressure will have
no effect
on the position of equilibrium.
Catalysts have
no effect
on position of equilibrium but speed up the
rate
at which equilibrium is achieved
Catalysts
work by providing an alternative reaction pathway wiith lower activation energy
Activation energy
: The
minimum
amount of
energy
needed for a
reaction
to occur with
successful collisions
The
larger
the Kc the greater the amount of products
Temperature
is the only external condition that affects value of Kc?
Give an essential condition for an
equilibrium
mixture:
Equilibrium occurs in a
closed system
(where reactants and products cannot escape)
In this equation, what effect would increasing the temperature have on the position of equilibrium?
The equilibrium position shifts to the
right.
(This is because the forward reaction is
endothermic.
Yield of hydrogen increases.)
What effect would increasing the pressure have on the position of equilibrium?
The equilibrium position shifts to the
left.
This is because the
forward reaction
is produces more
moles
of gas than the reverse reaction.
What effect does a catalyst have on the position of equilibrium?
No
effect
What type of system is Kc relevant for?
Homogeneous
systems in
equilibrium
What effect does decreasing the temperature in an exothermic reaction have on K c ?
K c
increases
What effect does increasing the temperature in an exothermic reaction have on K c ?
K c
decreases