1. Chemical Equilibrium
A reversible reaction can go in either the forward or reverse directions A + B C D +
Equilibrium is dynamic
as both the forward and reverse reactions continue
At equilibrium the forward and reverse rates are equal

2. Le Chateliers Principle
If a stress is applied to a system at equilibrium, the system adjusts to relieve the stress
CoCl42-
H2O
Co(H2O)62+ +
4Cl- +
H= -
H= +
Exothermic (Heating)
Endothermic ( Cooling)

3. CrO42- Cr2O72- Le Chatelier’s Principle
If a stress is applied to a system at equilibrium, the system adjusts to relieve the stress
CrO42-
Cr2O72- +
H2O
2H+ +

4. Fe(CNS)2- FeCl3 Le Chateliers Principle
If a stress is applied to a system at equilibrium, the system adjusts to relieve the stress
Fe(CNS)2-
FeCl3 +
CNS- +
3Cl-

5. Le Chatelier’s Principle
CoCl42-
H2O
Co(H2O)62+ +
4Cl- +
H= +
H= -
Exothermic (Heating)
Endothermic ( Cooling)
What happens if the red solution is heated ?
Heating is a stress
Le Chatelier states the opposing reaction occurs
The cooling reaction occurs
ie the reverse reaction
Turning red into blue

6. Haber process 2 NH3 N2 3 H2 NH3 N2 H2
Manufacture of ammonia NH3 for the fertilizer industry
2 NH3 N2
3 H2 H= + 2
NH3
Kc = 3 N2 H2 x

7. Haber process
Manufacture of ammonia NH3 for the fertilizer industry
2 NH3 N2
3 H2 H= +
Le Chatelier’s principle predicts the yield of NH3 is maximised by
Low temperature
High pressure
Actual temp used is 500oC (as lower temp reduces the rate )
Pressure used is 200 ATM

8. Contact process Manufacture of Sulfuric acid H2SO4 2 SO3 2SO2 O2+
Le Chatelier’s principle predicts the yield of SO3 is maximised by
Low temperature
High pressure
Actual temp used is 450 oC (as low temp reduces the rate )
Pressure used is 1 ATM