67. NCERT Exemplar XXXX

  

The four ions involved are $Na^+$, $CO_3^2{^–}$, $Ca^2{^+}$ and $Cl^–$. The combinations of the $Na^+$ and $Cl^–$ and the $Ca^2{^+}$ and $CO_3^2{^–}$ produce the compounds $NaCl$ and $CaCO_3$. If both of these compounds are mixeddissolvesolubleinsoluble, no reaction takes place. In this case,  however, $CaCO_3$ is solublemixeddissolveinsoluble. Thus a reaction occurs that we can illustrate with a balanced reaction written in molecular form.

$Na_2CO_3$(aq) + $CaCl_2$(aq) → $CaCO_2$(s)$NaCO_3$(s)$CaCO_3$(s)$NaCO_2$(s) + $CaCO_2$(s)$NaCl_2$(s)$NaCO_3$(s)$2NaCl_2$(aq)

 

The equation written in total ionic form is

 

$2Na^+$(aq) + $CO_3^2{^–}$(aq) + $Ca^2{^+}$(aq) + $2Cl^–$(aq) → $CaCO_3$(s) + $2Na^+$ + $2Cl^–$.

 

The net ionic equation will be $Ca^2{^+}$(aq) + $CO_3^2{^–}$(aq) → $NaCO_3$(s)$CaCO_3$(s)$NaCO_2$(s)$CaCO_2$(s).