This Grade 12 IEB Physical Science guide on chemical equilibrium covers Le Chatelier’s principle, dynamic equilibrium, and interpreting equilibrium constants (Kc) with temperature changes. It includes practice with equilibrium graphs and an understanding of shifts in equilibrium conditions, makin...
· reaction that increases concentration of removed substance
is favoured
Chemical equilibrium Le Chateliers Principle :
occurs when z reversible Catalyst is added
·
dynamic chemical equilibrium :
· define :
When an external stress (change, · both reaction rates increase by the same amount
processes are occuring simultaneously at the same rate concentration
In
,
temperature or
pressure
Idenoted with double half arrow ->> is applied to a system in chemical equl . E quilibrium Constant (Kc)
· open system both matter
and heat :
can enter and leave system librium
,
the equilibrium point will change in · KC depends on temperature only ,
If temperature changes
· closed system
:
only heat can escape/enter the system such a
way as to counteract stress KC will change .
endothermic
example N 0x(g) =
2NOz(g) It indicates to what extent the reactants have
changed
(AH)0))
:
= ·
becaus
effects of different disturbances on equilibrium :
into products by the time equilibrium is established
- refers to forward
reaction
Temperature increased :
· Must use concentrations at
equilibrium
rate of reaction
·
both reaction rates increase
1 .
e)aA + bB - c) + dD then kc = [A]
*
x[B]b
· endothermic reaction is favored (DH) 0
remember as Ke =
[products] (C) x [D]9
·
If forward reaction is endothermic KC increases
[reactants]
,
formed faster
being decreases
· If forward reaction is exothermic ,
KC
time · K 1 :
(products]< Creactants] ·
temperature decreased ↳ The higher the value of Ke the higher
Chemical closed system
the
yeild of the reaction
·
dynamic equilibrium : in a ,
both reaction rates decrease [reactants]
forward reaction
· 0 kc < 1 :
<products] <
the rate of the is equal to the rate
exothermic reaction is favored ↳ The lower the value of Kc the lower the yelld of the reaction
· ,
of the reverse reaction
o if forward reaction endothermic ; le decreases
Note :
When equilibrium is established the ,
amounts of note :
homogenous equilibrium
-
products and reactants in same phase
· If forward reaction exothermic ; KC increases
both reactants and products remain constant different
heterogenous equilibrium -
products and reactants in phases
pressure increased
NO c ·
both reaction rates increase
amount N204 · reaction that produces feler moles of
gas
(mol)
-
(determined by · is favoured
mole ratio
pressure decreased
time
·
both reaction rates decrease
· factors affecting dynamic chemical equilibrium , reaction that produces more moles of
the following factors can the favoured
external change rate
gas is
of reaction
↓ 2) of reactant (s) or product(s) increased
concentration (aq) and
(g)
- both reaction rates increase
temperature ·
-
pressure (g) · reaction that lowers (J of added substance is
(disturb equilibrium as they will
change rate of reaction) favoured
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