Chapter 9, Problem 30E

Interpretation Introduction

Interpretation:

Net ionic reaction for the precipitation reaction if occurs for $\text{Co}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)+{\text{K}}_{\text{3}}{\text{PO}}_{\text{4}}\left(\text{aq}\right)$ is to be stated.

Concept introduction:

Precipitation reaction are the reactions in which an insoluble compound is produced when solution of two ionic compounds are mixed. The insoluble compound formed settles down at the bottom and is known as precipitate.

Answer to Problem 30E

The net ionic reaction for the precipitation reaction between $\text{Co}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)+{\text{K}}_{\text{3}}{\text{PO}}_{\text{4}}\left(\text{aq}\right)$ is given below.

${\text{3Co}}^{2+}\left(\text{aq}\right)+2{\text{PO}}_4^{3-}\left(\text{aq}\right)\to {\text{Co}}_3{\left({\text{PO}}_{\text{4}}\right)}_2\left(\text{s}\right)$

Explanation of Solution

In the precipitation reactions, combination of ions and formation of insoluble products takes place. Therefore, if some ions are mixed together and their combination can lead to the formation of insoluble ionic compounds, then it is said that precipitation reaction has occurred and the product thus formed is known as precipitate.

The precipitation reaction for the reaction $\text{Co}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)+{\text{K}}_{\text{3}}{\text{PO}}_{\text{4}}\left(\text{aq}\right)$ occurs because the ion combination of ${\text{Co}}^{2+}\left(\text{aq}\right)$ and ${\text{PO}}_4^{3-}\left(\text{aq}\right)$ leads to formation of an insoluble ionic compound ${\text{Co}}_3{\left({\text{PO}}_{\text{4}}\right)}_2\left(\text{s}\right)$.

The reaction that occurs is shown below.

$\text{Co}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)+{\text{K}}_{\text{3}}{\text{PO}}_{\text{4}}\left(\text{aq}\right)\to {\text{Co}}_3{\left({\text{PO}}_{\text{4}}\right)}_2\left(\text{s}\right)+{\text{KNO}}_{\text{3}}\left(\text{aq}\right)$

Balance cobalt on both sides of the equation.

$\text{3Co}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)+{\text{K}}_{\text{3}}{\text{PO}}_{\text{4}}\left(\text{aq}\right)\to {\text{Co}}_3{\left({\text{PO}}_{\text{4}}\right)}_2\left(\text{s}\right)+{\text{KNO}}_{\text{3}}\left(\text{aq}\right)$

Balance phosphate on both sides of the equation.

$\text{3Co}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)+2{\text{K}}_{\text{3}}{\text{PO}}_{\text{4}}\left(\text{aq}\right)\to {\text{Co}}_3{\left({\text{PO}}_{\text{4}}\right)}_2\left(\text{s}\right)+{\text{KNO}}_{\text{3}}\left(\text{aq}\right)$

Balance potassium on both sides of the equation.

$\text{3Co}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)+2{\text{K}}_{\text{3}}{\text{PO}}_{\text{4}}\left(\text{aq}\right)\to {\text{Co}}_3{\left({\text{PO}}_{\text{4}}\right)}_2\left(\text{s}\right)+6{\text{KNO}}_{\text{3}}\left(\text{aq}\right)$

The net balanced chemical reaction is shown below.

$\text{3Co}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)+2{\text{K}}_{\text{3}}{\text{PO}}_{\text{4}}\left(\text{aq}\right)\to {\text{Co}}_3{\left({\text{PO}}_{\text{4}}\right)}_2\left(\text{s}\right)+6{\text{KNO}}_{\text{3}}\left(\text{aq}\right)$

The ionic equation for the above reaction is as follows.

$3{\text{Co}}^{2+}\left(\text{aq}\right)+6{\text{NO}}_3^{-}\left(\text{aq}\right)+6{\text{K}}^{+}\left(\text{aq}\right)+2{\text{PO}}_4^{3-}\left(\text{aq}\right)\to 6{\text{NO}}_3^{-}\left(\text{aq}\right)+6{\text{K}}^{+}\left(\text{aq}\right)+{\text{Co}}_3{\left({\text{PO}}_{\text{4}}\right)}_2\left(\text{s}\right)$ The net ionic reaction for the above reaction is as follows.

The common ions on both sides cancel out.

${\text{3Co}}^{2+}\left(\text{aq}\right)+2{\text{PO}}_4^{3-}\left(\text{aq}\right)\to {\text{Co}}_3{\left({\text{PO}}_{\text{4}}\right)}_2\left(\text{s}\right)$

Conclusion

The net ionic reaction for the precipitation reaction between $\text{Co}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)+{\text{K}}_{\text{3}}{\text{PO}}_{\text{4}}\left(\text{aq}\right)$ is as follows:

${\text{3Co}}^{2+}\left(\text{aq}\right)+2{\text{PO}}_4^{3-}\left(\text{aq}\right)\to {\text{Co}}_3{\left({\text{PO}}_{\text{4}}\right)}_2\left(\text{s}\right)$