Question

Decide whether a reaction occurs for each of the following. If it does not, write \(N R\) after the arrow. If it does, write the balanced molecular equation; then write the net ionic eauation. (a) \(\mathrm{Al}(\mathrm{OH})_{3}+\mathrm{HNO}_{3} \longrightarrow\) (b) \(\mathrm{NaBr}+\mathrm{HClO}_{4} \longrightarrow\) (c) \(\mathrm{CaCl}_{2}+\mathrm{NaNO}_{3} \longrightarrow\) (d) \(\mathrm{MgSO}_{4}+\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2} \longrightarrow\)

Short answer

(a) Balanced: \(\mathrm{Al(OH)}_3 + 3\mathrm{HNO}_3 \rightarrow \mathrm{Al(NO}_3)_3 + 3\mathrm{H}_2\mathrm{O}\); Net ionic: \(\mathrm{Al(OH)}_3 + 3\mathrm{H}^+ \rightarrow \mathrm{Al}^{3+} + 3\mathrm{H}_2\mathrm{O}\). (b) NR; (c) NR; (d) Balanced: \(\mathrm{MgSO}_{4} + \mathrm{Ba(NO}_{3})_{2} \rightarrow \mathrm{BaSO}_{4}\downarrow + \mathrm{Mg(NO}_{3})_{2}\); Net ionic: \(\mathrm{Ba}^{2+}+\mathrm{SO}_{4}^{2-}\rightarrow\mathrm{BaSO}_{4}\downarrow\).

Step-by-step solution

Analyze Reaction (a)

Reaction (a) involves \(\mathrm{Al}(\mathrm{OH})_{3}\) and \(\mathrm{HNO}_{3}\). Aluminum hydroxide is a base and nitric acid is an acid. This combination suggests a neutralization reaction. \(\mathrm{Al}(\mathrm{OH})_3\) reacts with \(\mathrm{HNO}_3\) to form \(\mathrm{Al(NO}_3)_3\) and \(\mathrm{H}_2\mathrm{O}\). The balanced equation is: \[\mathrm{Al}(\mathrm{OH})_3 + 3\mathrm{HNO}_3 \rightarrow \mathrm{Al(NO}_3)_3 + 3\mathrm{H}_2\mathrm{O}\] The net ionic equation involves removing the spectator ions to yield: \[\mathrm{Al(OH)}_3 + 3\mathrm{H}^+ \rightarrow \mathrm{Al}^{3+} + 3\mathrm{H}_2\mathrm{O}\]

Analyze Reaction (b)

In reaction (b), we have \(\mathrm{NaBr}\) and \(\mathrm{HClO}_{4}\). \(\mathrm{NaBr}\) is a salt and \(\mathrm{HClO}_{4}\) is a strong acid. There are no driving forces (such as a formation of a precipitate, gas, or weak electrolyte). Thus, no reaction occurs, so we write \(\mathrm{NR}\) after the arrow.

Analyze Reaction (c)

For reaction (c), we have \(\mathrm{CaCl}_{2}\) and \(\mathrm{NaNO}_{3}\). Both compounds dissolve completely in water to give ions. No precipitate, gas, or weak electrolyte is formed when these ions mix. Therefore, no reaction takes place. We denote this with \(\mathrm{NR}\) after the arrow.

Analyze Reaction (d)

Reaction (d) involves \(\mathrm{MgSO}_{4}\) and \(\mathrm{Ba(\mathrm{NO}_{3})}_{2}\). Mixing these compounds results in the formation of \(\mathrm{BaSO}_{4}\), a precipitate. Thus, a reaction occurs. Balanced molecular equation: \[\mathrm{MgSO}_{4} + \mathrm{Ba(NO}_{3})_{2} \rightarrow \mathrm{BaSO}_{4}\downarrow + \mathrm{Mg(NO}_{3})_{2}\] Net ionic equation is: \[\mathrm{Ba}^{2+}+\mathrm{SO}_{4}^{2-}\rightarrow\mathrm{BaSO}_{4}\downarrow\]

Key concepts

Net Ionic Equations

A net ionic equation provides a clearer picture of the ions participating directly in a chemical reaction. It strips out the spectator ions—those ions that do not participate in the actual chemical change and remain in solution unchanged. This kind of equation offers a simplified version of what's truly occurring at the ionic level.

To write a net ionic equation, follow these steps:

• First, write the balanced molecular equation for the reaction.
• Next, break all the strong electrolytes (soluble salts, strong acids, and bases) into their ions.
• Identify and remove spectator ions that appear unchanged on both sides of the reaction.
• What remains is the net ionic equation, showcasing only the ions involved in the formation of the product.

In reaction (a) of the exercise, the net ionic equation is \[\mathrm{Al(OH)}_3 + 3\mathrm{H}^+ \rightarrow \mathrm{Al}^{3+} + 3\mathrm{H}_2\mathrm{O}\]
Where here, \(\mathrm{H}^+\) ions from nitric acid and neutralize the \(\mathrm{OH}^-\) ions from the aluminum hydroxide, showing the true ionic participants of the reaction.

Balanced Molecular Equations

Balanced molecular equations convey the full chemical reaction with all reactants and products shown in their molecular form. Balancing these equations is crucial, as it ensures that the law of conservation of mass is followed, meaning the number of atoms of each element on the reactant side equals those on the product side.

To balance a molecular equation:

• Count the number of atoms for each element on both sides of the equation.
• Adjust the coefficients (the numbers before the compounds) to balance the atoms for each element.
• Ensure that the equation is balanced both in terms of atoms and charge.

For example, in the given exercise, the balanced molecular equation for reaction (a) is:\[\mathrm{Al} (\mathrm{OH})_3 + 3 \mathrm{HNO}_3 \rightarrow \mathrm{Al (NO}_3)_3 + 3 \mathrm{H}_2 \mathrm{O}\]Here, the equation is balanced with three units of nitric acid reacting with aluminum hydroxide, producing aluminum nitrate and water, adhering to the conservation of mass.

Precipitate Formation

Precipitate formation is a key indicator that a chemical reaction has occurred in a solution. A precipitate is an insoluble solid that forms when two aqueous solutions combine and form a product that does not dissolve in water.

The formation of a precipitate can be predicted using solubility rules, which provide guidelines on which ionic compounds are soluble or insoluble in water. When two ionic solutions are mixed and an insoluble compound forms, it will precipitate out of the solution as a solid.

In the exercise, reaction (d) highlights precipitate formation. When \(\mathrm{MgSO}_4 + \mathrm{Ba (NO}_3)_2 \) are mixed, \(\mathrm{BaSO}_4 \) forms as a precipitate:\[\mathrm{Ba}^{2+} + \mathrm{SO}_4^{2-} \rightarrow \mathrm{BaSO}_4 \downarrow\]The solid \(\mathrm{BaSO}_4 \) sinks out of the solution. This occurrence confirms a chemical reaction has taken place, driven by the formation of a solid precipitate.

Neutralization Reactions

Neutralization reactions are a specific type of chemical reaction where an acid and a base react to form water and an ionic compound, often called a salt. This type of reaction is characterized by the exchange of ions, where hydrogen ions \(\mathrm{H}^+\) from the acid combine with hydroxide ions \(\mathrm{OH}^-\) from the base, forming water-due to the attraction between opposite charges.

Neutralization is important in various chemical processes, including those in industry, environmental science, and biological systems. These reactions are generally exothermic, meaning they release heat.

In the exercise, reaction (a) is an example of a neutralization reaction, where \(\mathrm{Al(OH)}_3\), a base, reacts with \(\mathrm{HNO}_3\), an acid, forming \(\mathrm{Al(NO}_3)_3\) and water:\[\mathrm{Al(OH)}_3 + 3\mathrm{HNO}_3 \rightarrow \mathrm{Al(NO}_3)_3 + 3\mathrm{H}_2\mathrm{O}\]Understanding neutralization reactions helps in predicting the products of acid-base reactions and is essential for applications such as titration in laboratories.