Consider a Solution Consisting of the Following Two Buffer Systems

Multiple Choice

Consider a solution consisting of the following two buffer systems:
H₂CO₃
HCO₃^- + H⁺ pK_a = 6.4
H₂PO₄^-
HPO₄^2- + H⁺ pK_a = 7.2
At pH 6.4, which one of the following is true of the relative amounts of acid and conjugate base present?

A) [H₂CO₃] > [HCO₃^-] and [H₂PO₄^-] > [HPO₄^2-]
B) [HCO₃^-] > [H₂CO₃] and [HPO₄^2-] > [H₂PO₄^-]
C) [H₂CO₃] > [HCO₃^-] and [HPO₄^2-] > [H₂PO₄^-]
D) [H₂CO₃] = [HCO₃^-] and [HPO₄^2-] > [H₂PO₄^-]
E) [H₂CO₃] = [HCO₃^-] and [H₂PO₄^-] > [HPO₄^2-]