On the basis of the information below, a buffer with a pH =9 can best be made by using?

Question

Acid Acid Dissociation Constant,Ka

H3PO4 7.0 x 10-3

H2P04 8.0 X 10-8

HPO42 5.0 X 10-

a. pure NaH2PO4

b. H3PO4 + H2PO4-

c. H2PO4- + P043-

d. H2PO4- + HPO4-

e. HPO42- + PO43-

Answer 1

Acid Acid Dissociation Constant,Ka

H3PO4 7.0 x 10-3

H2P04 8.0 X 10-8

HPO42 5.0 X 10-13



your answer is d. H2PO4- + HPO4-

the acid H2PO4- has a pKa the closest to the desired pH, ....

& its conjugate base is HPO4)-2