Reversible Reactions

Question 1

Will Reversible Reactions reach Equilibrium?

Answer 1

Yes

As reactants react, their concentrations fall - so the forward reaction will slow down. But as more and more products are made and their concentrations rise, the backward reaction will speed up.

After while forward reaction will be going exactly the same rate as the backward one - the system is at equilibrium.

At equilibrium both reactions still happening but there’s no overall effect (it’s a dynamic equilibrium). This means the concentrations of reactants and products have reached a balance and won’t change.

Equilibrium is only reached if the reversible reaction takes place in a ‘closed system’. A closed system just means that none of the reactants or products can escape and nothing else can get in.

Question 2

Can the position of Equilibrium can be on the right or the left?

Answer 2

Yes

Equilibrium lies to the right, the concentration of products is greater than that of the reactants

Equilibrium lies to the left, the concentration of reactants is greater than that of the products

Question 3

Reversible reactions can be Endothermic and Exothermic!

Answer 3

The energy transferred from the surroundings by the endothermic reaction is equal to the energy transferred to the surroundings during the exothermic reaction.

A good example is the Thermal Decomposition if Hydrated Copper Sulfate:

                                   Endothermic Hydrated Copper Sulfate > Anhydrous Copper Sulfate + 
                                       <                                        Water
                                   Exothermic

If you heat blue hydrated copper sulfate crystals, it drives the water off and leaves white anhydrous copper sulfate powder. This is endothermic

If you then add a couple of drops of water to the white powder you get the blue crystals back again. This is exothermic.