Consider the curve shown here for the titration of a weak base with a strong acid and answer each question.

d. At what volume of added acid is the pH calculated by working an equilibrium problem based on the concentration and K_a of the conjugate acid?

Video transcript

Hello. In this problem we are told. The image below shows the titillation of a weak base with a strong acid. Were asked to determine the volume of added acid where the equilibrium concentration of the species in solution and the K. Of the conjugate acid is used to calculate the ph let's begin by writing our reaction that occurs with the titillation of a weak base with a strong acid. So here we have our base and our strong acid. So the strong acid will donate a proton to our base, inform H. B and a minus. So H. B. Then is the conjugate acid of our weak base. At the equivalence point, then we've added enough acid to completely react with our weak base. So all that's left. Then at the equivalence point are the products of this reaction are conjugate acid. Then we'll undergo hydraulic sis so it will donate a proton to water real form b minus and high joining mines. So we have an equilibrium situation. Then that exists at the equivalence point we can write our acid dissociation constant which would be the concentration of our products over the concentration of our reactant and water being a pure liquid is eliminated from this expression. So at the equivalence point then we can find the ph we create a nice table. We can determine the hydrogen ion concentration and from that the ph and so we are making use of our equilibrium concentrations and the K. Value for our conjugate acid to determine the ph And this again occurs at the equivalence point. So the volume of added acid. Then at the equivalence point we can find by looking at our titillation plot that's where we have this inflection point. If we followed that down, we find then the volume of added acid to reach. The equivalence point is 11 milliliters, and so this is our volume where the ph will be determined from the concentration of species in solution, as well as the value for a conjugate acid. And this corresponds. And to answer C. Thanks for watching. Hope this help.