Determine what happens to the pH (increases, decreases, or remains the same) of a buffer solution containing equal concentrations of C₆H₇O₇⁻ and C₆H₆O₇²⁻on the addition of each of the following: 
(a) K₃C₆H₅O₇
(b) NaBr
(c) C₆H₈O₇
(d) HCl 
(e) K₂C₆H₆O₇ 
(f) NaOH

• A. (a) increases
  (b) remains the same
  (c) decreases
  (d) remains the same
  (e) decreases
  (f) increases
• B. (a) increases
  (b) decreases
  (c) increases
  (d) remains the same
  (e) decreases
  (f) decreases
• C. (a) decreases
  (b) remains the same
  (c) increases
  (d) decreases
  (e) decreases
  (f) increases
• D. (a) increases
  (b) remains the same
  (c) decreases
  (d) decreases
  (e) increases
  (f) increases

Answer: (D)