Question

Consider the following endothermic equilibrium system in a closed container. In which direction will the equilibrium shift with each of the disturbances listed below? HCO3-(s) + HC2H3O2 (aq) ↔ C2H3O2-(aq) + H2O (aq) + CO2 (g)

a. adding CO2 (g) .

b. adding NaOH (aq) .

c. adding H+ (aq) .

d. placing it in an ice bath.

e. opening the container.

Answer 1

Le Chatelier's Principle states that if the equilibrium is disturbed, the reaction will proceed in the direction so as to restore the equilibrium. So, we will analyse each case one by one and decide the direction of the equilibrium. It's given that the reaction is endothermic and in a closed container.

a. Adding CO2: On adding CO2, the reaction will want to decrease the amount of CO2, hence it will move towards the reactants side.

b. Adding NaOH: when sodium hydroxide is added, it will react with acetic acid to produce acetate and water. Both the product is increasing in concentration and the reactant is decreasing in concentration, therefore the equilibrium will shift towards reactant side.

c. Adding H+: Acetate would be converted back to acetic acid on addition of H+, therefore the equilibrium would move in the forward direction, i.e. towards the products side.

d. Placing it in an ice bath: Since the forward reaction is endothermic, the backward reaction will be exothermic by the same amount. So when the temperture is dereassed, the reaction will try to generate the heat to maintain the temperture, therefore it will move towards the reactant side.

e. Opening the container: CO2 would be released when the container is opened. Therefore the reaction would move in the forward direction (towards the products) in order to maintain the equilibrium.