Given the values of Ka and Kb below, which of the systems given would be most suitable to use to construct a buffer of pH 9?
HCOOH, Ka = 1.8 x 10-4
CH3COOH, Ka = 1.8 x 10-5
H3AsO4, Ka1 = 6.0 x 10-3, Ka2 = 1.1 x 10-7, Ka3 = 3 x 10-12
C5H5N, Kb = 1.7 x 10-9
NH3, Kb = 1.8 x 10-5
A. H3AsO4/NaH2AsO4
B. HCOOH/NaHCOO
C. C5H5N/ C5H5NHCl
D. CH3COOH/KCH3COO
E. NH4Cl/NH3