1. Module 3 Lesson 12/13 Reversible Reactions & Dynamic Equilibria

2. Objectives Must State that some chemical reactions are reversible Should Describe how reversible reactions reach a state of equilibrium Could Explain how at dynamical equilibrium the rate of the forward reaction is equal to the rate of the reverse reaction. Must State that some chemical reactions are reversible Should Describe how reversible reactions reach a state of equilibrium Could Explain how at dynamical equilibrium the rate of the forward reaction is equal to the rate of the reverse reaction.

3. Reversible or not reversible Until now, we were careful to say that most chemical reactions were not reversible – They could not go back to the reactants once the products are formed.

4. Example

5. Reversible Some chemical reactions, however, will go backwards and forwards depending on the conditions. CoCl 2 ·6H 2 O(s)  CoCl 2 (s) + 6H 2 O(l) pink blue

6. How do we write them down? This is the symbol for used for reversible reactions. CoCl 2 ·6H 2 O(s) CoCl 2 (s) + 6H 2 O(l)

7. What is equilibrium?

8. General equation This is the equation for a general reaction which has reached dynamic equilibrium: How did it reach this balanced state

12. Eventually, the rates of the two reactions will become equal. A and B will be converting into C and D at exactly the same rate as C and D convert back into A and B again

14. Dynamic Equilibrium.

15. Other examples 2NO 2  N 2 O 4 Briggs Rauscher Briggs Rauscher – an awesome set of 10 competing chemical reactions in equilibrium

16. Plenary - Examination questions As a warm up we will use some GCSE level answers.

19. Mark scheme

20. Summary State that some chemical reactions are reversible Describe how reversible reactions reach a state of equilibrium Explain this using dynamic equilibrium model. State that some chemical reactions are reversible Describe how reversible reactions reach a state of equilibrium Explain this using dynamic equilibrium model.