Q4.31P - 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) Sodium nitrate + copper(II) sulfate 

(b) Ammonium bromide + silver nitrate

Step-by-Step Solution

Answer

(a) Precipitation reaction does not occur.

(b) A precipitation reaction occurs.

Step 1: Write the equation of sodium nitrate and copper(II) sulfate

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

(a)$2{\mathrm{NaNO}}_3\left(\mathrm{aq}\right)+{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)\to {\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)$

Since these compounds are soluble in  aqueous solvent 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 bromide and silver nitrate

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:

(b) ${\mathrm{NH}}_4\mathrm{Br}\left(\mathrm{aq}\right)+{\mathrm{AgNO}}_3\left(\mathrm{aq}\right)\to {\mathrm{NH}}_4{\mathrm{NO}}_3\left(\mathrm{aq}\right)+\mathrm{AgBr}\left(\mathrm{s}\right)$

The total ionic equation is:

${\mathrm{NH}}_4^{+}\left(\mathrm{aq}\right)+{\mathrm{Br}}^{-}\left(\mathrm{aq}\right)+{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{NO}}_3^{-}\left(\mathrm{aq}\right)\to {\mathrm{NH}}_4^{+}\left(\mathrm{aq}\right)+{\mathrm{NO}}_3^{-}\left(\mathrm{aq}\right)+\mathrm{AgBr}\left(\mathrm{s}\right)$

The net ionic equation is:

${\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Br}}^{-}\left(\mathrm{aq}\right)\to \mathrm{AgBr}\left(\mathrm{s}\right)$

Since, silver bromide is insoluble in aqueous solution, precipitate is formed.