To study the effects of a weakly acidic medium on the rate of corrosion of a metal alloy, a student prepared a buffer solution containing both 0.193 M NaC2H3O2 and 0.072 M HC2H3O2. Calculate the pH of the buffer using the Kb for C2H3O2-. Be sure to write the chemical equation for the equilibrium as the reaction of C2H3O2- with water. Then use the chemical equation as a guide in setting up the equilibrium expression for Kb. For acetic acid, HC2H3O2, Ka