Question

Write net ionic equations for the reaction of \(\mathrm{H}^{+}\) with (a) \(\mathrm{Fe}_{2} \mathrm{~S}_{3}\) (b) \(\mathrm{Mg}(\mathrm{OH})_{2}\) (c) \(\mathrm{MgCO}_{3}\) (d) \(\operatorname{Pt}\left(\mathrm{NH}_{3}\right)_{4}^{2+}\) (e) \(\mathrm{Hg}_{2} \mathrm{I}_{2}\)

Short answer

In this exercise, the net ionic equations for the given reactions are as follows: (a) Reaction of \(\mathrm{H}^+\) with \(\mathrm{Fe}_2 \mathrm{S}_{3}\): $$\mathrm{6H^+ + Fe_2S_3 \rightarrow 2Fe^{3+} + 3H_2S}$$ (b) Reaction of \(\mathrm{H}^+\) with \(\mathrm{Mg(OH)_2}\): $$\mathrm{2H^+ + 2OH^- \rightarrow 2H_2O}$$ (c) Reaction of \(\mathrm{H}^+\) with \(\mathrm{MgCO_3}\): $$\mathrm{2H^+ + CO_3^{2-} \rightarrow H_2O + CO_2}$$ (d) Reaction of \(\mathrm{H}^+\) with \(\operatorname{Pt}\left(\mathrm{NH}_{3}\right)_{4}^{2+}\): $$\mathrm{2H^+ + Pt(NH_3)_4^{2+} \rightarrow Pt(NH_3)_4^{4+} + 2NH_4^+}$$ (e) Reaction of \(\mathrm{H}^+\) with \(\mathrm{Hg_2 \mathrm{I}_2}\): $$\mathrm{4H^+ + Hg_2I_2 \rightarrow 2Hg^{2+} + 4I^- + 2H_2}$$

Step-by-step solution

(a) Reaction of \(\mathrm{H}^+\) with \(\mathrm{Fe}_2 \mathrm{S}_{3}\)

The balanced chemical equation for the reaction of \(\mathrm{H}^+\) ions with \(\mathrm{Fe}_2 \mathrm{S}_{3}\) is: $$\mathrm{6H^+ + Fe_2S_3 \rightarrow 2Fe^{3+} + 3H_2S}$$ The net ionic equation for this reaction is the same, as all the ions are involved in the reaction. So the net ionic equation is: $$\mathrm{6H^+ + Fe_2S_3 \rightarrow 2Fe^{3+} + 3H_2S}$$

(b) Reaction of \(\mathrm{H}^+\) with \(\mathrm{Mg(OH)_2}\)

The balanced chemical equation for the reaction of \(\mathrm{H}^+\) ions with \(\mathrm{Mg(OH)_2}\) is: $$\mathrm{2H^+ + Mg(OH)_2 \rightarrow Mg^{2+} + 2H_2O}$$ The net ionic equation for this reaction, after removing the spectator ions, is: $$\mathrm{2H^+ + 2OH^- \rightarrow 2H_2O}$$

(c) Reaction of \(\mathrm{H}^+\) with \(\mathrm{MgCO_3}\)

The balanced chemical equation for the reaction of \(\mathrm{H}^+\) ions with \(\mathrm{MgCO_3}\) is: $$\mathrm{2H^+ + MgCO_3 \rightarrow Mg^{2+} + H_2O +CO_2}$$ The net ionic equation for this reaction, after removing the spectator ions, is: $$\mathrm{2H^+ + CO_3^{2-} \rightarrow H_2O + CO_2}$$

(d) Reaction of \(\mathrm{H}^+\) with \(\operatorname{Pt}\left(\mathrm{NH}_{3}\right)_{4}^{2+}\)

The balanced chemical equation for the reaction of \(\mathrm{H}^+\) ions with \(\operatorname{Pt}\left(\mathrm{NH}_{3}\right)_{4}^{2+}\) is: $$\mathrm{2H^+ + Pt(NH_3)_4^{2+} \rightarrow Pt(NH_3)_4^{4+} + 2NH_4^+}$$ The net ionic equation for this reaction, after removing the spectator ions, is: $$\mathrm{2H^+ + Pt(NH_3)_4^{2+} \rightarrow Pt(NH_3)_4^{4+} + 2NH_4^+}$$ Note that the net ionic equation is identical to the balanced chemical equation in this case, as all ions are involved in the reaction.

(e) Reaction of \(\mathrm{H}^+\) with \(\mathrm{Hg_2 \mathrm{I}_2}\)

The balanced chemical equation for the reaction of \(\mathrm{H}^+\) ions with \(\mathrm{Hg_2 \mathrm{I}_2}\) is: $$\mathrm{4H^+ + Hg_2I_2 \rightarrow 2Hg^{2+} + 4I^- + 2H_2}$$ The net ionic equation for this reaction is the same, as all the ions are involved in the reaction. So the net ionic equation is: $$\mathrm{4H^+ + Hg_2I_2 \rightarrow 2Hg^{2+} + 4I^- + 2H_2}$$

Key concepts

Understanding Chemical Reactions

Chemical reactions are processes where substances, also known as reactants, are transformed into new substances, called products. They involve the breaking and formation of chemical bonds and are usually represented by chemical equations. One important type of chemical equation is the net ionic equation, which shows only the species that participate directly in the reaction, excluding spectator ions.

For instance, in the reactions provided, substances like \(\mathrm{Mg(OH)_2}\) and \(\mathrm{H}^+\) react to form new products such as \(\mathrm{Mg^{2+}}\) and water. By focusing on the ions that change during the reaction, the net ionic equation simplifies the process to its core components, making it clearer which species are involved and how they interact.

In learning to write net ionic equations, students become adept in identifying the reactants and products, balancing chemical equations, and understanding the flow of electrons during a reaction.

Acid-Base Reactions Simplified

Acid-base reactions are a subset of chemical reactions where an acid donates a proton (\(\mathrm{H}^+\)) to a base. These reactions are prevalent in many scientific fields and everyday life. Writing net ionic equations for acid-base reactions helps to illustrate the direct exchange occurring between the acidic and basic ions.

For example, when \(\mathrm{H}^+\) reacts with \(\mathrm{Mg(OH)_2}\), a base, it results in the formation of water (\(\mathrm{H_2O}\)) and magnesium ions (\(\mathrm{Mg^{2+}}\)). The net ionic equation for this reaction is \(2\mathrm{H}^+ + 2\mathrm{OH}^- \rightarrow 2\mathrm{H_2O}\), which concisely depicts the essential part of the reaction. By focusing on the exchange of the proton, one can easily recognize and classify the reaction as an acid-base reaction.

Solubility Rules Uncovered

Solubility rules are guidelines used to predict whether an ionic compound is likely to dissolve in water. They are a fundamental concept when writing net ionic equations because they determine which compounds dissolve to form ions and which remain as precipitates.

For instance, common rules state that most nitrate \(\mathrm{(NO_3^-)}\) salts are soluble, while many sulfide \(\mathrm{(S^{2-})}\) salts are not. This knowledge enables us to accurately predict the outcome of reactions. In the exercises provided, compounds like \(\mathrm{MgCO_3}\) and \(\mathrm{Fe}_2\mathrm{S}_3}\) do not fully dissolve in water, which is important for writing the correct net ionic equations.

With a strong grasp of solubility rules, students can efficiently decode complex reactions to their net ionic forms, as these guidelines directly affect which components of the reaction will be visibly participating in the actual chemical change.