Chapter 11.3, Problem 33LC

Interpretation Introduction

Interpretation: The complete and net ionic reaction of calcium ion and magnesium ions present in hard water with sodium phosphate is to be stated.

Concept Introduction : According to the law of conservation of mass, the mass can neither be created nor to be destroyed. Every reaction must be balanced.

Answer to Problem 33LC

The complete and net ionic reaction of calcium ion and magnesium ions present in hard water with sodium phosphate is:

With calcium ion: ${\text{3Ca}}^{2+}\left(aq\right)+2{\text{Na}}_3{\text{PO}}_4\left(aq\right)\to {\text{Ca}}_3{\left({\text{PO}}_4\right)}_2\left(s\right)+6{\text{Na}}^{+}\left(aq\right)$ and ${\text{3Ca}}^{2+}\left(aq\right)+2{\text{PO}}_4{}^{3-}\left(aq\right)\to {\text{Ca}}_3{\left({\text{PO}}_4\right)}_2\left(s\right)$

With magnesium ion: ${\text{3Mg}}^{2+}\left(aq\right)+2{\text{Na}}_3{\text{PO}}_4\left(aq\right)\to {\text{Mg}}_3{\left({\text{PO}}_4\right)}_2\left(s\right)+6{\text{Na}}^{+}\left(aq\right)$ and ${\text{3Mg}}^{2+}\left(aq\right)+2{\text{PO}}_4{}^{3-}\left(aq\right)\to {\text{Mg}}_3{\left({\text{PO}}_4\right)}_2\left(s\right)$

Explanation of Solution

The reaction of calcium ion with sodium phosphate is given as follows:

  ${\text{3Ca}}^{2+}\left(aq\right)+2{\text{Na}}_3{\text{PO}}_4\left(aq\right)\to {\text{Ca}}_3{\left({\text{PO}}_4\right)}_2\left(s\right)+6{\text{Na}}^{+}\left(aq\right)$

The ionic equation is given as:

  ${\text{3Ca}}^{2+}\left(aq\right)+6{\text{Na}}^{+}\left(aq\right)+2{\text{PO}}_4{}^{3-}\left(aq\right)\to {\text{Ca}}_3{\left({\text{PO}}_4\right)}_2\left(s\right)+6{\text{Na}}^{+}\left(aq\right)$

The ions present on both sides are known as spectators’ ions and these ions are excluded in net ionic equation. The balanced net ionic equation is given as:

  ${\text{3Ca}}^{2+}\left(aq\right)+2{\text{PO}}_4{}^{3-}\left(aq\right)\to {\text{Ca}}_3{\left({\text{PO}}_4\right)}_2\left(s\right)$

Similarly, the reaction of magnesium ion with sodium phosphate is given as follows:

  ${\text{3Mg}}^{2+}\left(aq\right)+2{\text{Na}}_3{\text{PO}}_4\left(aq\right)\to {\text{Mg}}_3{\left({\text{PO}}_4\right)}_2\left(s\right)+6{\text{Na}}^{+}\left(aq\right)$

The ionic equation is given as:

  ${\text{3Mg}}^{2+}\left(aq\right)+6{\text{Na}}^{+}\left(aq\right)+2{\text{PO}}_4{}^{3-}\left(aq\right)\to {\text{Mg}}_3{\left({\text{PO}}_4\right)}_2\left(s\right)+6{\text{Na}}^{+}\left(aq\right)$

The ions present on both sides are known as spectators’ ions and these ions are excluded in net ionic equation. The balanced net ionic equation is given as:

  ${\text{3Mg}}^{2+}\left(aq\right)+2{\text{PO}}_4{}^{3-}\left(aq\right)\to {\text{Mg}}_3{\left({\text{PO}}_4\right)}_2\left(s\right)$