Problem 42 - Chemistry The Central Science

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.

Step-by-Step Solution

Answer

The net ionic equations for the reactions are: (a) \[\mathrm{FeO(s)} + 2\mathrm{H^+(aq)} \longrightarrow \mathrm{Fe^{2+}(aq)} + \mathrm{H_2O(l)}\] (b) \[\mathrm{NiO(s)} + 2\mathrm{H^+(aq)} \longrightarrow \mathrm{Ni^{2+}(aq)} + \mathrm{H_2O(l)}\]

Step 1: Part (a): Net Ionic Equation for the reaction between FeO and HClO₄

First, we need to write the balanced chemical equation, which is already given as: \[\mathrm{FeO(s)} + 2 \mathrm{HClO_4(aq)} \longrightarrow \mathrm{Fe(ClO_4)_2(aq)} + \mathrm{H_2O(l)}\] Next, we'll break this balanced chemical equation into the corresponding ionic equation. In order to do this, we must identify the correct ionic forms of the compounds that are dissolved in the aqueous solution: \[\mathrm{FeO(s)} + 2\mathrm{H^+(aq)} + 2\mathrm{ClO_4^-(aq)} \longrightarrow \mathrm{Fe^{2+}(aq)} + 2\mathrm{ClO_4^-(aq)} + \mathrm{H_2O(l)}\] Now, let's write the net ionic equation by canceling out the spectator ions (the ions that remain unchanged during the course of the reaction). In this case, the spectator ions are the \(\mathrm{ClO_4^-}\) ions: \[\mathrm{FeO(s)} + 2\mathrm{H^+(aq)} \longrightarrow \mathrm{Fe^{2+}(aq)} + \mathrm{H_2O(l)}\] Thus, the net ionic equation for the reaction between \(\mathrm{FeO}\) and \(\mathrm{HClO_4}\) is: \[\mathrm{FeO(s)} + 2\mathrm{H^+(aq)} \longrightarrow \mathrm{Fe^{2+}(aq)} + \mathrm{H_2O(l)}\]

Step 2: Part (b): Net Ionic Equation for the reaction between NiO and an aqueous solution of nitric acid

Based on the reaction in part (a), we can write the net ionic equation for the reaction between \(\mathrm{NiO(s)}\) and an aqueous solution of nitric acid (\(\mathrm{HNO_3}\)). The overall reaction is: \[\mathrm{NiO(s) + 2 HNO_3(aq) \longrightarrow Ni(NO_3)_2(aq) + H_2 O(l)}\] Breaking the equation into the ionic equation, we get: \[\mathrm{NiO(s)} + 2\mathrm{H^+(aq)} + 2\mathrm{NO_3^-(aq)} \longrightarrow \mathrm{Ni^{2+}(aq)} + 2\mathrm{NO_3^-(aq)} + \mathrm{H_2O(l)}\] Now, let's write the net ionic equation by canceling out the spectator ions (the ions that remain unchanged during the reaction). In this case, the spectator ions are the \(\mathrm{NO_3^-}\) ions: \[\mathrm{NiO(s)} + 2\mathrm{H^+(aq)} \longrightarrow \mathrm{Ni^{2+}(aq)} + \mathrm{H_2O(l)}\] Thus, the net ionic equation for the reaction between \(\mathrm{NiO}\) and an aqueous solution of nitric acid (\(\mathrm{HNO_3}\)) is: \[\mathrm{NiO(s)} + 2\mathrm{H^+(aq)} \longrightarrow \mathrm{Ni^{2+}(aq)} + \mathrm{H_2O(l)}\]

Key Concepts

Acid-Base Reactions

In chemistry, acid-base reactions are fundamental processes in which an acid reacts with a base to produce a salt and water. They are also known as neutralization reactions. The acid contributes hydrogen ions ( \( ext{H}^+ \) ) while the base provides hydroxide ions ( \( ext{OH}^- \) ), resulting in the formation of water.

• The acid donates a proton (a hydrogen ion), which is accepted by the base.
• This results in the neutralization of the acid and base, forming water (\(\text{H}_2\text{O}\)) as a product. The cation from the base and the anion from the acid combine to form a salt.

For the reactions involving metal oxides, such as iron(II) oxide ( \( ext{FeO} \) ) or nickel(II) oxide ( \( ext{NiO} \) ), these oxides act as strong bases that readily react with acids. This concept is evident in the problem where \( ext{FeO} \) reacts with \( ext{HClO}_4 \) , producing a salt and water.
As a result, the oxide ion \( ext{O}^{2-} \) accepts protons ( \( ext{H}^+ \) ) from the acid to form water, effectively neutralizing the acid. Understanding these reactions is crucial for comprehending how different substances interact in aqueous solutions.

Spectator Ions

In many chemical reactions, some ions are present in the solution but do not participate directly in the transformation. These are called spectator ions. They simply "watch" the reaction happen, hence the name.
Their presence does not affect the balance or the end result of the chemical reaction. For instance, in the reaction between \( ext{FeO} \) and \( ext{HClO}_4 \) , the \( ext{ClO}_4^- \) ions do not interact with the reactants or products. Hence, during the formation of the net ionic equation, we can safely ignore them.

• Spectator ions remain unchanged on both the reactant and the product sides of the ionic equation.
• Eliminating them from the equation simplifies it, highlighting the actual chemical reaction occurring. This is known as the net ionic equation.

For example, the net ionic equation for the metal oxide and nitric acid reaction excludes the nitrate ions ( \( ext{NO}_3^- \) ), focusing only on the components that change during the process. This approach is beneficial when exploring the essential chemical dynamics of reactions.

Metal Oxides

Metal oxides play a significant role in chemistry, particularly in reactions with acids. They are typically basic, meaning they tend to accept protons and neutralize acids.

• Most metal oxides are formed from a metallic element and oxygen, characterized by the general formula \( ext{MO}_x \).
• These compounds can act as basic anhydrides. So, when dissolved in water or reacting with an acid, they form bases.

In the given exercise, metal oxides such as \( ext{FeO} \) and \( ext{NiO} \) are reacting with acids like perchloric acid ( \( ext{HClO}_4 \) ) and nitric acid ( \( ext{HNO}_3 \) ), forming salts and water.
When these oxides react with acids, the oxide ions ( \( ext{O}^{2-} \) ) pair with hydrogen ions ( \( ext{H}^+ \) ) from the acids to form water, illustrating their nature as strong bases. Understanding the behavior of metal oxides helps to predict the products of acid-base reactions, thereby deepening the comprehension of chemical interactions.