Question

Trisodium phosphate $\left(\text{TSP}\right)$is an effective grease remover. Like many cleaners,$\mathbf{\text{TSP}}$acts as a base in water. Write a balanced equation to account for this basic behaviour.

Short answer

The balanced equation for the basic behaviour of $\text{TSP}$when it reacts with water is ${\text{PO}}_{\text{4}}^{\text{3 -}}{\text{(aq) +H}}_{\text{2}}\text{O(l)}\rightleftharpoons {\text{HPO}}_{\text{4}}^{\text{2 -}}{\text{(aq) + OH}}^{\text{-}}\text{(aq)}$.

Step-by-step solution

Concept Introduction

A chemical equation in which the overall charge and the number of atoms for each element in the reaction are the same for both the reactants and the products is called as balanced chemical equation.

Balanced equation for TSP

Trisodium phosphate is the inorganic compound with chemical formula${\text{Na}}_{\text{3}}{\text{PO}}_{\text{4}}$.

Phosphate is derived from phosphoric acid by the removal of three protons${\text{H}}^{\text{+}}$ .

Phosphate is the conjugate base of weak acid${\text{HPO}}_{\text{4}}^{\text{2 -}}$(mono-hydrogen phosphate ion).

As it is known, all conjugate bases of weak acids are effective bases.

The reaction of${\text{PO}}_{\text{4}}^{\text{3 -}}$and water is shown below –

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

The base dissociation constant for reaction shown above is $\text{2.1}·{\text{10}}^{\text{- 2}}$.

Since, a large${\text{K}}_{\text{b}}$ , value means a base has largely dissociated and indicates a strong base.

Therefore, the balanced equation is ${\text{PO}}_{\text{4}}^{\text{3 -}}{\text{(aq) +H}}_{\text{2}}\text{O(l)}\rightleftharpoons {\text{HPO}}_{\text{4}}^{\text{2 -}}{\text{(aq) + OH}}^{\text{-}}\text{(aq)}$.