Thus a greater proportion of the c2h3o2 in buffer 1

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Unformatted text preview: equilibrium-constant expression for the dissociation of acetic acid. [HC2 H3O2 ] − [C2 H 3O 2 ] = [H + ] Ka After the addition of the H+, the ratio in buffer 1 must have been greater than the corresponding ratio in buffer 2, as evidenced by their respective pH values. Thus a greater proportion of the C2H3O2− in buffer 1 must have reacted with the added H+ compared to the proportion that reacted in buffer 2. The difference between these proportions means that the original concentrations of HC2H3O2 and C2H3O2− had to be smaller in buffer 1 than in buffer 2. One point is earned for a correct answer involving better buffering capacity or relative amount of base (acetate ion). © 2007 The College Board. All rights reserved. Visit apcentral.collegeboard.com (for AP professionals) and www.collegeboard.com/apstudents (for students and parents). AP® CHEMISTRY 2007 SCORING GUIDELINES (Form B) Question 5 (continued) (iii) Explain why the pH of buffer 1 is the same as the pH of buffer 2 before 0.10 mol of HCl is...
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This note was uploaded on 10/01/2009 for the course OC 9876 taught by Professor Dq during the Spring '09 term at UC Merced.

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