Phosphoric acid is a triprotic acid with the following pKa values: pKa1=2.148, p
ID: 822420 • Letter: P
Question
Phosphoric acid is a triprotic acid with the following pKa values:
pKa1=2.148, pKa2=7.198, pKa3=12.375
You wish to prepare 1.000 L of a 0.0500 M phosphate buffer at pH 7.540. To do this, you choose to mix the two salt forms involved in the second ionization, NaH2PO4 and Na2HPO4, in a 1.000 L volumetric flask and add water to the mark. What mass of each salt will you add to the mixture?
Mass NaH2PO4
Mass Na2HPO4
What other combination of phosphoric acid and/or its salts could be mixed to prepare this buffer? (Check all that apply).
H3PO4 and NaH2PO4
H3PO4 and Na2HPO4
H3PO4 and Na3HPO4
NaH2PO4 and NA3PO4
Na2HPO4 and NA3PO4
PLEASE SOLVE AND EXPLAIN
Explanation / Answer
H3PO4 + Na2HPO4
H3PO4 + Na3PO4
NaH2PO4 + Na3PO4
These will all make suitable buffers for the average of their Ka will be around 7