Chapter 9.1, Problem 13SSC

Interpretation Introduction

Interpretation:

The balanced chemical equation of reaction of aqueous phosphoric acid and aqueous calcium hydroxide to form solid calcium phosphate and water needs to be determined.

Concept introduction:

The chemical equation is the way of writing chemical reaction with the help of chemical formulas of the reactants and products. To write the chemical equation, one must know the chemical formulas of products and reactants. The chemical equation is the balanced equation.

Answer to Problem 13SSC

The chemical equation is,

${\text{2H}}_{\text{3}}{\text{PO}}_{\text{4}}(aq)+3{\text{Ca(OH)}}_2(aq)\to {\text{Ca}}_{\text{3}}{{\text{(PO}}_{\text{4}})}_2(s)+6{\text{H}}_{\text{2}}\text{O}\text{(}l\text{)}$

Explanation of Solution

The chemical formula of phosphoric acid is ${\text{H}}_{\text{3}}{\text{PO}}_{\text{4}}$ and chemical formula of calcium hydroxide is ${\text{Ca(OH)}}_{\text{2}}$ and calcium phosphate is ${\text{Ca}}_3{{\text{(PO}}_4\text{)}}_{\text{2}}$.

So, the skeleton equation for the reaction is,

${\text{H}}_{\text{3}}{\text{PO}}_{\text{4}}(aq)+{\text{Ca(OH)}}_2(aq)\to {\text{Ca}}_{\text{3}}{{\text{(PO}}_{\text{4}})}_2(s)+{\text{H}}_{\text{2}}\text{O}\text{(}l\text{)}$

The above equation is not a balanced equation. Chemical equation follows law of conservation of mass. So, the balanced equation is,

${\text{2H}}_{\text{3}}{\text{PO}}_{\text{4}}(aq)+3{\text{Ca(OH)}}_2(aq)\to {\text{Ca}}_{\text{3}}{{\text{(PO}}_{\text{4}})}_2(s)+6{\text{H}}_{\text{2}}\text{O}\text{(}l\text{)}$