Question

A phosphate buffer solution at a pH = pK1 = 2.15 would have equal amounts of phosphate in the ____________ form and the H2PO4(1-) form.

a) HPO₄(2-) form
b) H₂PO₄(1-) form
c) H₃PO₄ form
d) PO₄(3-) form

Answer 1

In a phosphate buffer solution with pH equal to pK1, the concentrations of H₃PO₄ and H₂PO₄¹⁻ are equal.

Step-by-step explanation:

A phosphate buffer solution at a pH = pK1 = 2.15 would have equal amounts of phosphate in the H₃PO₄ form and the H₂PO₄1- form. The correct answer is c) H₃PO₄ form. In the context of phosphate buffer systems, the pK1 value refers to the dissociation constant of the first proton from phosphoric acid (H₃PO₄), resulting in the dihydrogen phosphate ion (H₂PO₄1-). When the pH of the solution is equal to the pK1, the concentrations of H₃PO₄ and H₂PO₄1- are equal, thus maintaining a buffered solution.