Question

Write a net ionic equation for the reaction with aqueous \(\mathrm{NH}_{3}\) in which (a) \(\mathrm{Pt}^{2+}\) forms a complex ion. (b) \(\mathrm{Ag}^{+}\) forms a precipitate. (c) \(\mathrm{Ni}(\mathrm{OH})_{3}\) dissolves.

Short answer

Question: Provide the net ionic equations for the following reactions with aqueous ammonia (NH₃): a) Formation of Pt²⁺ complex ion b) Formation of Ag⁺ precipitate c) Dissolution of Ni(OH)₃ Answer: a) \(\mathrm{Pt}^{2+} + 4\mathrm{NH}_3 \rightleftharpoons \mathrm{[Pt(NH}_3)_4]^{2+}\) b) \(\mathrm{Ag}^{+} + 2\mathrm{OH}^-\rightleftharpoons \mathrm{Ag}_2\mathrm{O}\) c) \(\mathrm{Ni(OH)_3} + 3\mathrm{NH}_3 + 3\mathrm{H}_2\mathrm{O} \rightleftharpoons \mathrm{[Ni(NH}_3)_3(H_2O)_3]^{3+} + 3\mathrm{OH}^-\)

Step-by-step solution

Formation of Pt²⁺ complex ion with NH₃

Write the balanced chemical equation for the reaction: The reaction between Pt²⁺ ions and NH₃ will form a complex ion. In this case, Pt²⁺ forms a coordination complex with NH₃ as ligand. \(\mathrm{Pt}^{2+} + 4\mathrm{NH}_3 \rightleftharpoons \mathrm{[Pt(NH}_3)_4]^{2+}\) Here we have used the square brackets to represent the formation of a complex ion.

Find the net ionic equation for Pt²⁺ complex formation

The net ionic equation is the same as the balanced chemical equation as we don't have any spectator ions. \(\mathrm{Pt}^{2+} + 4\mathrm{NH}_3 \rightleftharpoons \mathrm{[Pt(NH}_3)_4]^{2+}\)

Formation of Ag⁺ precipitate with NH₃

Write the balanced chemical equation for the reaction: The reaction between Ag⁺ ions and NH₃ will form a silver complex ion, which then reacts further with OH⁻ to form a precipitate of Ag₂O. First, we need to know the balanced equation for the formation of the silver complex ion: \(\mathrm{Ag}^{+} + 2\mathrm{NH}_3 \rightleftharpoons \mathrm{[Ag(NH}_3)_2]^{+}\) Upon reacting with OH⁻ ions, the silver complex ion will break down to form Ag₂O precipitate and release NH₃ back into the solution: \(\mathrm{[Ag(NH}_3)_2]^{+} + 2\mathrm{OH}^-\rightleftharpoons \mathrm{Ag}_2\mathrm{O} + 4\mathrm{NH}_3\)

Find the net ionic equation for Ag⁺ precipitate formation

Combine the balanced equations and rearrange to get the net ionic equation: \(\mathrm{Ag}^{+} + 2\mathrm{NH}_3 + 2\mathrm{OH}^-\rightleftharpoons \mathrm{Ag}_2\mathrm{O} + 4\mathrm{NH}_3\) Remove the spectator species (2NH₃) from the equation: \(\mathrm{Ag}^{+} + 2\mathrm{OH}^-\rightleftharpoons \mathrm{Ag}_2\mathrm{O}\)

Dissolution of Ni(OH)₃ with NH₃

Write the balanced chemical equation for the reaction: The reaction between Ni(OH)₃ and NH₃ will form a complex ion, which dissolves in the solution. \(\mathrm{Ni(OH)_3} + 3\mathrm{NH}_3 + 3\mathrm{H}_2\mathrm{O} \rightleftharpoons \mathrm{[Ni(NH}_3)_3(H_2O)_3]^{3+} + 3\mathrm{OH}^-\)

Find the net ionic equation for the dissolution of Ni(OH)₃

The net ionic equation for this reaction is the same as the balanced chemical equation as we don't have any spectator ions. \(\mathrm{Ni(OH)_3} + 3\mathrm{NH}_3 + 3\mathrm{H}_2\mathrm{O} \rightleftharpoons \mathrm{[Ni(NH}_3)_3(H_2O)_3]^{3+} + 3\mathrm{OH}^-\)