Buffer Systems Help?

Question

What would an equation be to show how a buffer made up of equimolar amounts of acetic acid, CH3COOH, and acetate, CH3Coo-, would behave when HCl was added and then when NaOH is added?

Answer 1

Ka = [H+][C2H3O2-]/[HC2H3O2] = 1.8 x 10^-5

In each case, you solve for [H+]. This is because:

HCl + C2H3O2- ===> HC2H3O2 + Cl-

which increases the amount of essentially unionized HC2H3O2 in the denominator and decreases the amount of C2H3O2- in the numerator; and:

NaOH + HC2H3O2 ===> Na+C2H3O2- + H2O

which decreases the HC2H3O2 in the denominator while increasing the C2H3O2- in the numerator.