Question

A) what is the definition of an "amhiprotic" substance?

B) Illustrate with two equations how the dihydrogen phosphate anion is amphiprotic:

C) Validate/illustrate your answer to part (B) with two balanced equations and their Keqs.

D)Would a solution of potassium dihydrogen phophate be acidic or basic?

Answer 1

Answer –

A)The amphiprotic substance are the substance which can acts as acid and base, means they are either donate H⁺ or accept H⁺. When this compound acts as base when reacting with acid and acts as acid when reacting with base.

B) We know the amphiprotic substance play role acid as well as base. In the dihydrogen phosphate anion means H₂pO₄^- act as acid by donating H⁺ and formed HPO₄^2- or it can act as base by accepting H⁺ and formed H₃pO₄.

So following are the two equations for the amphiprotic nature of dihydrogen phosphate anion-

Act as acid -

H₂PO₄^- <-------> HPO₄^2- + H⁺  

Act as base -

H₂PO₄^- + H⁺   <-------> H₃PO₄

C) When dihydrogen phosphate anion reacts with water, so it acts as amphiprotic substance and reaction are as follow -

H₂PO₄^- + H₂O <-------> HPO₄^2- + H₃O⁺

H₂PO₄^- + H₂O <-------> H₃PO₄ + OH^-

So Ka = [HPO₄^2-] H₃O⁺] / [H₂PO₄^-]

Kb = [H₃PO₄] [OH^-] / [H₂PO₄^-]

D) A solution of potassium dihydrogen phophate be acidic, because there if it take H⁺ then its acidic increase and when it donate H⁺ then also it has remaining 1 more proton. So there is resulting solution is acidic.