Question

Because the oxide ion is basic, metal oxides react readily with acids. (a) Write the net ionic equation for the following reaction: $$ \mathrm{FeO}(s)+2 \mathrm{HClO}_{4}(a q) \longrightarrow \mathrm{Fe}\left(\mathrm{ClO}_{4}\right)_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) $$ (b) Based on the equation in part (a), write the net ionic equation for the reaction that occurs between \(\mathrm{NiO}(s)\) and an aqueous solution of nitric acid.

Short answer

(a) The net ionic equation for the reaction between FeO and HClO4 is: \( FeO(s) + 2 H^+(aq) \longrightarrow Fe^{2+}(aq) + H_2O(l) \) (b) The net ionic equation for the reaction between NiO and nitric acid is: \( NiO(s) + 2 H^+(aq) \longrightarrow Ni^{2+}(aq) + H_2O(l) \)

Step-by-step solution

Identify the strong electrolytes

In the given reaction, we need to identify the strong electrolytes, which are HClO4. Strong electrolytes dissociate into their ions completely in an aqueous solution.

Dissociate the strong electrolytes into their ions

The strong electrolyte HClO4 can be dissociated as follows: \( 2 HClO_4 \longrightarrow 2 H^+ + 2 ClO_4^- \) For FeO, it should be noted that we cannot dissociate it into its ions because it is a solid metal oxide.

Write the complete ionic equation

Now, write the complete ionic equation by replacing the strong electrolytes with their dissociated ions: \( FeO (s) + 2 H^+ (aq) + 2 ClO_4^- (aq) \longrightarrow Fe^{2+} (aq) + 2 ClO_4^- (aq) + H_2O (l) \)

Identify and remove the spectator ions

Observe the complete ionic equation to identify the spectator ions. In this case, the spectator ion is ClO4-. Spectator ions are the ions that remain the same in the reactants and products. They can be removed to write the net ionic equation.

Write the net ionic equation

Remove the spectator ions and write the net ionic equation for the given reaction: \( FeO(s) + 2 H^+(aq) \longrightarrow Fe^{2+}(aq) + H_2O(l) \) Now, let's move on to part (b) of the exercise. (b):

Write the balanced reaction equation between NiO and nitric acid

The balanced reaction between NiO (s) and nitric acid (HNO3) can be written as: \( NiO(s) + 2 HNO_3(aq) \longrightarrow Ni(NO_3)_2(aq) + H_2O(l) \)

Identify the strong electrolytes and dissociate them

Nitric acid (HNO3) is a strong electrolyte. It dissociates into its ions completely in an aqueous solution: \( 2 HNO_3 \longrightarrow 2 H^+ + 2 NO_3^- \)

Write the complete ionic equation

Now, we can write the complete ionic equation: \( NiO(s) + 2 H^+(aq) + 2 NO_3^-(aq) \longrightarrow Ni^{2+}(aq) + 2 NO_3^-(aq) + H_2O(l) \)

Identify and remove the spectator ions

The spectator ion in this reaction is NO3-. By removing the spectator ions, we can write the net ionic equation.

Write the net ionic equation

Remove the spectator ions and write the net ionic equation for the reaction between NiO and nitric acid: \( NiO(s) + 2 H^+(aq) \longrightarrow Ni^{2+}(aq) + H_2O(l) \)

Key concepts

Strong Electrolytes

Strong electrolytes are substances that completely dissociate into ions when dissolved in water. This complete dissociation means that they conduct electricity well in solution because there are many free ions to carry the charge. A good example from the exercise is perchloric acid,
often represented as HClO₄, and nitric acid,
HNO₃. Both are strong acids and thus, strong electrolytes. When they dissolve in water, they break down completely into their constituent ions:
- HClO₄ dissociates into H⁺ and ClO₄⁻ ions. - HNO₃ dissociates into H⁺ and NO₃⁻ ions. Knowing that a substance is a strong electrolyte helps in predicting the outcome of reactions, particularly when writing balanced and net ionic equations.

Spectator Ions

In chemical reactions, spectator ions are ions present in solution that do not participate in the reaction. They remain unchanged during the process. Identifying these ions is crucial while writing net ionic equations because they are eliminated from the equation, simplifying it to show only the reacting species.
Take the initial reaction for example: After dissociating HClO₄, the ClO₄⁻ ions do not engage in the chemical change and are therefore spectator ions. Similarly, in the reaction involving NiO and HNO₃, the NO₃⁻ ions are spectator ions because they do not take part in the central reaction between NiO and H⁺ ions.
Removing spectators, like ClO₄⁻ and NO₃⁻, helps us focus on the essential chemical changes, making it clearer to understand what actually happens in a reaction.

Metal Oxides

Metal oxides, such as FeO and NiO in the given problems, are solid compounds formed by metals bonded with oxygen. These oxides often exhibit basic characteristics, especially when interacting with acids.
In acidic reactions, these metal oxides typically undergo transformations where they react with hydrogen ions ( H⁺) provided by the acidic solution, forming water and the soluble metal ions:

• FeO reacts with H⁺ ions to produce Fe²⁺ ions and water.
• NiO reacts with H⁺ ions to yield Ni²⁺ ions and water.

These reactions with metal oxides are key to forming the net ionic equations by showing only the necessary species. The metal ions in such reactions change their oxidation state, indicating a transfer of electrons, which is an essential part of understanding redox reactions and acid-base behavior of oxides.