Q4.33P - Chemistry: Molecular Nature Of Matter And Change

Question

When each of the following pairs of aqueous solutions is mixed, does a precipitation reaction occur? If so, write balanced molecular, total ionic, and net ionic equations.

(a) Potassium chloride + iron (III) nitrate 

(b) Ammonium sulfate + barium chloride

Step-by-Step Solution

Answer

(a) Precipitation reaction does not occur.

(b) Precipitation reaction occurs. The precipitate formed is Barium sulfate.

Step 1: Write the equation of potassium chloride and iron (III) nitrate

We note the ions present in the reactants for each pair of solutions and write the cation-anion combinations if any of them are insoluble or soluble. For the molecular equation, we predict the products:

$\left(\mathrm{a}\right)3\mathrm{KCl}\left(\mathrm{aq}\right)+\mathrm{Fe}{\left({\mathrm{NO}}_3\right)}_3\left(\mathrm{aq}\right)\to {\mathrm{FeCl}}_3\left(\mathrm{aq}\right)+3{\mathrm{KNO}}_3\left(\mathrm{aq}\right)$

Since these compounds are soluble in aqueous solution  hence this reaction does not give a precipitate

All ammonium, sodium, and most perchlorate compounds are soluble, and all bromides, nitrates are soluble except those of Ag⁺, Pb²⁺, Cu⁺, and Hg₂²⁺.

Therefore, the compounds remain dissociated in the solution as solvated ions.

Step 2: Write the equation of ammonium sulfate and barium chloride

For each pair of solutions, we note the ions present in the reactants and write the cation-anion combinations if any of them are insoluble or soluble. For the molecular equation, we predict the products:

The balanced molecular reaction is:

${\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+{\mathrm{BaCl}}_2\left(\mathrm{aq}\right)\to 2{\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{aq}\right)+{\mathrm{BaSO}}_4\left(\mathrm{s}\right)$

The total ionic equation is:

 $2{\mathrm{NH}}_4^{+}\left(\mathrm{aq}\right)+{\mathrm{SO}}_4^{2-}\left(\mathrm{aq}\right)+{\mathrm{Ba}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)\to 2{\mathrm{NH}}_4^{+}\left(\mathrm{aq}\right)+2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)+{\mathrm{BaSO}}_4\left(\mathrm{s}\right)$

The net ionic equation is:

${\mathrm{Ba}}^{2+}\left(\mathrm{aq}\right)+{\mathrm{SO}}_4^{2-}\left(\mathrm{aq}\right)\to {\mathrm{BaSO}}_4\left(\mathrm{s}\right)$

Barium sulfate formed is insoluble in aqueous solution and hence forms precipitate.