Correct question:
A 0.10 M solution of Na2HPO4 could be made a buffer solution with all of the following EXCEPT ________.
K3PO4
Na3PO4
H3PO4
NaH2PO4
Answer:
K3PO4
Explanation:
A buffer is an aqueous solution that can resist large changes in pH by virtue of its components, which is a weak acid and its conjugate base, or a weak base and its conjugate acid.
In other words, they should be conjugate acid of the weak base or conjugate base of the weak acid.
Na2HPO4 could function as a weak monobasic acid to give out its proton to form Na2PO4- and this could also be represented by the Na3PO4...which is the salt of the weak acid.
It could also function as a base by accepting proton to form NaH2PO4 which is the conjugate acid (if Na2HPO4 functions as base). They are a conjugate pair.
This is the same reason with H3PO4 which is the Conjugate acid of Na2HPO4.
So it could be a conjugate pair with those 3, except K3PO4.
