Topic 6b : Reversible Reactions

what is a reversible reaction ?

what is a reversible reaction ?

A reversible reaction is one where the products of the reaction can themselves react to produce the original reactants

Give a visual representation of a reversible reaction ?

A + B (=) C + D

what is equilibrium ?

this is when the amounts of reactants and products are balanced

is a reversible reaction at equilibrium ?

if a reversible reaction takes place in a closed system then a state of equilibrium will always be reached

what is a closed system ?

this means that none of the reactants or products can escape and nothing else can get in

what is the overall outcome of a reversible reaction ?

both reactions are still happening but the overall effect is nil (net-0 effect) because the forward and reverse reaction cancel each other out

in a reversible reaction at equilibrium is the amount of products and reactants always equal ?

• if the equilibrium lies to the right , the concentration of the products is greater than that of the reactants

• if the equilibrium lies to the left , the concentration of the reactants is greater than that of the products

in a reversible reaction which of the forward and backward reaction is endothermic and the other exothermic ?

in a reversible reaction if the reaction is endothermic in one direction it will be exothermic in the other direction

describe a reversible reaction in terms of it’s energy ?

the energy absorbed by the endothermic reaction is equal to the energy released by the exothermic reaction

give 2 examples of a reversible reaction ? State their word equation :

• thermal decomposition of hydrated copper sulfate

  hydrated copper sulfate <=> anhydrous copper sulfate + water

• thermal decomposition of calcium carbonate

  calcium carbonate ( CaCO₃ ) <=> carbonate ( CaO ) + carbon dioxide ( CO_{2 )}

What is le Chatelier’s principle ?

it is the idea that if you can change the conditions of a reversible reaction at equilibrium , the system will try to counteract the change. This means the effect of any changes to a system can be predicted .So by altering the temperature, pressure, or concentration of the reactants - you can alter the yield of the reaction - making sure you end up with more of the product you want (and less of the reactants)