The document discusses the position of equilibrium in chemical reactions. It states that if a dynamic equilibrium is disturbed, the position of equilibrium will move to counteract the change according to Le Chatelier's principle. Specifically, it provides examples of how the equilibrium position would change if ammonia, hydrogen, or nitrogen were removed from the ammonia synthesis reaction, or if pressure or temperature were increased. It also notes that while catalysts speed up the rate of the reaction, they do not change the equilibrium position.

1. 7.2 The Position of Equilibrium
Deduce Kc
Le Chatelier’s Principle

3. Key Points thus far…
• A reaction is at equilibrium if :-
The rate of the forward reaction = the rate of the
backward reaction, therefore quantities remain
constant
Macroscopically there is no change however
microscopically there is constant change
Equilibria only exist in a CLOSED SYSTEM – from which no
energy exchange is possible
An equilibrium can favour products ( rhs ) or reactants
(lhs)

4. Kc and the Magnitude of Kc
• Kc is the equilibrium constant, where….
• When Kc>> 1, the reaction goes almost to
completion.
• When Kc<< 1, the reaction hardly proceeds.

5. Some Examples
• For the synthesis of an ester…….

6. OK give me another example
• Ammonia synthesis

7. And just one more
• Contact Process

8. Position of Equilibirum
• Consider Ammonia synthesis …..
• What will be the effect of removing Ammonia ?
• What will be the effect of adding Hydrogen ?

9. Le Chatelier’s Principle
• If a dynamic equilibrium is disturbed by
changing the conditions, the position of
equilibrium moves to counteract the change.
• If you remove something ( same as decreasing
concentration ) the equilibrium will seek to
replace it.

10. Good old Ammonia 
• Impact of removing
– 1. Ammonia
– 2. Hydrogen
– 3. Nitrogen
• Impact of increasing pressure ( GASES ONLY )
– As pressure is a consequence of the impact of gas
molecules on its container, the equilibrium will
shift to the side with LESS GAS MOLECULES to
counteract the change.

11. So What About Temperature ?
• This is a little more complicated.
• If exothermic
• If endothermic

12. Is that everything ?
• Well……..NO !
• Catalysts 
• A catalyst has absolutely no effect on the
position of equilibrium, it merely increases the
rate at which equilibrium is reached.

13. Back to the practical 