1. Many biochemical reactions are reversible
Reversible reactions
Learning Objectives:
To investigate reversible reactions.
Key words: reversible, condition, direction
Mg + 2HCl  MgCl2 + H2
Wood reacting with oxygen
Many biochemical reactions are reversible
Irreversible
Reversible

2. Reversible reactions and dynamic equilibrium
Learning Objectives:
To be able to write an equation to show a reversible reaction.
To know that reversible reactions can reach a state of equilibrium.
To know what dynamic equilibrium means.
Key words: dynamic equilibrium
Mg + 2HCl  MgCl2 + H2
Wood reacting with oxygen
Many biochemical reactions are reversible
Reversible
Irreversible

3. Simple reversible reactions
Heating copper sulphate
The change from blue hydrated copper sulphate to white anhydrous copper sulphate is one of the most commonly known reversible reactions.
Heat
anhydrous copper sulphate
CuSO4.5H  CuSO H2O
hydrated copper sulphate
steam

4. Heat Simple reversible reactions NH4Cl(s) NH3(g) + HCl(g)
Heating ammonium chloride
Ammonium salts are made by reacting ammonia with an acid but some of these salts will decompose back into reactants when heated.
ammonium chloride
ammonia
hydrogen chloride
NH4Cl(s) NH3(g) + HCl(g)
Heat
Heat makes the solid disappear as it changes into gases.
Solid reappears as it changes back again in the cool part of the tube.

5. A B A B Dynamic equilibrium
A reversible reaction is where products can, under appropriate conditions, turn back into reactants.
Range of conditions over which both the forward and backward reaction will take place. This can lead to a state of balance with both reactants and products present in unchanging amounts.
This is called a dynamic equilibrium. A B A B
these combine
these decompose

6. Equilibrium – unchanging amounts of reactants and products
Dynamic equilibrium
Equilibrium – unchanging amounts of reactants and products
Dynamic – the reaction is still occurring
Ac7.10 – Watch the demonstration and annotate the diagrams to describe dynamic equilibrium

7. Dynamic equilibrium
How can equilibrium be used to explain the difference between strong and weak acids? P

8. Chromatography as an application of dynamic equilibrium
Whilst your chromatogram is running:
Read p and make notes on the difference between strong and weak acids in terms of dynamic equilibrium.
Read p222 and explain why chromatography is an application of dynamic equilibrium.
Define the term Rf in relation to chromatography.