Question

Colculate the eghilie riam Constant in Concentrations of the acidi'c disso eackion Cconstant dissociatiort) of acetic acid if the eguilisniun constant is knoun that tle coettisientS of activity of eacl iohare egual

Answer 1

Equilibrium constant of the chemical reaction can be termed as the reaction quotient of that same reaction in which the froward reaction and backward reaction has attained a dynamic equilibrium.

Mathematically , it can be defined as the ratio of the concentration of the product species to the reactant species.

Chemical reaction of acetic acid dissolution can be written as -

                  CH₃COOH (l) + H₂O(aq) -------> CH3COO^-(aq) + H3O⁺(aq)

                       Ka = [CH3COO^-] [H3O⁺]   /    [CH₃COOH] [H₂O]

where Ka = dissociation constant of acetic acid.

Activity coefficient is represented by $\gamma$ and activity multiplied by this activity coefficient makes the concentration of any species.

Given that

pKa = 10^-4.7

As we know that pka = -log ka , Thus 10^-4.7 = - log Ka, taking anti logs of both sides, we can get the value of Ka which is found to be 7.31

Thus dissociation constant of acetic acid = 7.31

Therefore, equilibrium constant ,Keq = dissociation constant x activity coefficient

                                                        Keq = 7.31 x 0.9 = 6.579

Thus, equilibrium constant of the given reaction is 6.579.