Chapter 15, Problem 15.102QP

The dihydrogen phosphate ion has the ability to act as an acid in the presence of a base and as a base in the presence of an acid. What is this property called? Illustrate this behavior with water by writing Brønsted–Lowry acid–base reactions. Also illustrate this property by selecting a common acid and base to react with the dihydrogen phosphate ion.

Interpretation Introduction

Interpretation:

The behavior with water by writing Bronsted-Lowry acid base reactions of dihydrogen phosphare ion and also amphiprotic property by selecting a common strong acid and base to react with dihydrogen phosphare ion has to be illustrated.

Concept introduction:

Amphiprotic:

A molecule either by donating or accepting a proton, which will act as either as an acid or a base and this molecule is said to be amphiprotic.

For this property, water, amino acids, hydrogen carbonate ions and hydrogen sulfate ions are examples.

Answer to Problem 15.102QP

Illustration of amphiprotic behavior of dihydrogen phosphare ion with water is

${\text{H}}_{\text{2}}{\text{PO4}}^{\text{-}}{}_{\text{(aq)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\stackrel{}{\rightleftharpoons }{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{}_{\text{(aq) }}{\text{+ HPO}}_{\text{4}}{{}^{\text{2-}}}_{\text{(aq)}}$

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{{}^{\text{-}}}_{\text{(aq)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\stackrel{}{\rightleftharpoons }{\text{H}}_{\text{3}}{\text{PO}}_{\text{4(aq) }}{\text{+ OH}}^{\text{-}}{}_{\text{(aq)}}$

A common strong acid and base to react with the dihydrogen phosphare ion is

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{{}^{\text{-}}}_{\text{(aq)}}{\text{ + K}}^{\text{+}}{}_{\text{(aq)}}{\text{ + OH}}^{\text{-}}{}_{\text{(aq)}}\stackrel{}{\rightleftharpoons }{\text{K}}^{\text{+}}{}_{\text{(aq)}}{\text{ + HPO}}_{\text{4}}{{}^{\text{2-}}}_{\text{(aq) }}{\text{+ H}}_{\text{2}}{\text{O}}_{\text{(l)}}$

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{{}^{\text{-}}}_{\text{(aq)}}{\text{ + H}}^{\text{+}}{}_{\text{(aq)}}{\text{ + NO}}_{\text{3}}{{}^{\text{-}}}_{\text{(aq)}}\stackrel{}{\rightleftharpoons }{\text{H}}_{\text{3}}{\text{PO}}_{\text{4(aq)}}{\text{ + NO}}_{\text{3}}{{}^{\text{-}}}_{\text{(aq)}}$

Explanation of Solution

Illustration of amphiprotic behavior of dihydrogen phosphare ion with water by writing Bronsted-Lowry acid base reactions are

${\text{H}}_{\text{2}}{\text{PO4}}^{\text{-}}{}_{\text{(aq)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\stackrel{}{\rightleftharpoons }{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{}_{\text{(aq) }}{\text{+ HPO}}_{\text{4}}{{}^{\text{2-}}}_{\text{(aq)}}$

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{{}^{\text{-}}}_{\text{(aq)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\stackrel{}{\rightleftharpoons }{\text{H}}_{\text{3}}{\text{PO}}_{\text{4(aq) }}{\text{+ OH}}^{\text{-}}{}_{\text{(aq)}}$

dihydrogen phosphare ion can react with potassium ion for base presence and hydrogen ion for acid presence can be illustrated as fallows.

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{{}^{\text{-}}}_{\text{(aq)}}{\text{ + K}}^{\text{+}}{}_{\text{(aq)}}{\text{ + OH}}^{\text{-}}{}_{\text{(aq)}}\stackrel{}{\rightleftharpoons }{\text{K}}^{\text{+}}{}_{\text{(aq)}}{\text{ + HPO}}_{\text{4}}{{}^{\text{2-}}}_{\text{(aq) }}{\text{+ H}}_{\text{2}}{\text{O}}_{\text{(l)}}$

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{{}^{\text{-}}}_{\text{(aq)}}{\text{ + H}}^{\text{+}}{}_{\text{(aq)}}{\text{ + NO}}_{\text{3}}{{}^{\text{-}}}_{\text{(aq)}}\stackrel{}{\rightleftharpoons }{\text{H}}_{\text{3}}{\text{PO}}_{\text{4(aq)}}{\text{ + NO}}_{\text{3}}{{}^{\text{-}}}_{\text{(aq)}}$

Conclusion

Illustration of amphiprotic behavior of dihydrogen phosphare ion with water was

${\text{H}}_{\text{2}}{\text{PO4}}^{\text{-}}{}_{\text{(aq)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\stackrel{}{\rightleftharpoons }{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{}_{\text{(aq) }}{\text{+ HPO}}_{\text{4}}{{}^{\text{2-}}}_{\text{(aq)}}$

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{{}^{\text{-}}}_{\text{(aq)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\stackrel{}{\rightleftharpoons }{\text{H}}_{\text{3}}{\text{PO}}_{\text{4(aq) }}{\text{+ OH}}^{\text{-}}{}_{\text{(aq)}}$

A common strong acid and base to react with the dihydrogen phosphare ion was

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{{}^{\text{-}}}_{\text{(aq)}}{\text{ + K}}^{\text{+}}{}_{\text{(aq)}}{\text{ + OH}}^{\text{-}}{}_{\text{(aq)}}\stackrel{}{\rightleftharpoons }{\text{K}}^{\text{+}}{}_{\text{(aq)}}{\text{ + HPO}}_{\text{4}}{{}^{\text{2-}}}_{\text{(aq) }}{\text{+ H}}_{\text{2}}{\text{O}}_{\text{(l)}}$

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{{}^{\text{-}}}_{\text{(aq)}}{\text{ + H}}^{\text{+}}{}_{\text{(aq)}}{\text{ + NO}}_{\text{3}}{{}^{\text{-}}}_{\text{(aq)}}\stackrel{}{\rightleftharpoons }{\text{H}}_{\text{3}}{\text{PO}}_{\text{4(aq)}}{\text{ + NO}}_{\text{3}}{{}^{\text{-}}}_{\text{(aq)}}$