Problem 14 - Chemistry The Central Science In Si Units

Question

State whether each of the following statements is true or false. Justify your answer in each case. (a) When acetone, \(\mathrm{CH}_{3} \mathrm{COCH}_{3},\) is dissolved in water, a conducting solution results. (b) When ammonium nitrate, \(\mathrm{NH}_{4} \mathrm{NO}_{3},\) dissolves in water, the solution is weakly conducting and basic in nature.

Step-by-Step Solution

Answer

(a) False, (b) False.

Step 1: Evaluating Acetone Solution Conductivity

Acetone, \( \mathrm{CH}_3 \mathrm{COCH}_3 \), is a molecular compound that does not dissociate into ions when dissolved in water. Conducting solutions require free ions to carry electrical current. Since acetone does not ionize in water, its solution will not conduct electricity.

Step 2: Conclusion on Acetone

Since acetone does not ionize in water, the statement that it forms a conducting solution is false.

Step 3: Evaluating Ammonium Nitrate Solution Conductivity

Ammonium nitrate, \( \mathrm{NH}_4 \mathrm{NO}_3 \), is an ionic compound that dissociates completely into \( \mathrm{NH}_4^+ \) and \( \mathrm{NO}_3^- \) ions when dissolved in water. This results in a solution capable of conducting electricity, as the free ions act as charge carriers.

Step 4: Nature of Ammonium Nitrate Solution

Upon dissolving, \( \mathrm{NH}_4^+ \) and \( \mathrm{NO}_3^- \) do not produce any significant basic nature in the solution. \( \mathrm{NH}_4^+ \) is a weak acid and can slightly lower the pH, but it doesn't make the solution basic. Thus, the solution is conducting due to dissociation but not basic.

Step 5: Conclusion on Ammonium Nitrate

The statement that ammonium nitrate solution is weakly conducting and basic is false. It is strongly conducting but not basic.

Key Concepts

Conductivity

Conductivity refers to a solution's ability to carry an electric current, which is primarily facilitated by ions. When a substance dissolves in water and releases positively and negatively charged ions, these ions move freely and allow the conduction of electricity. Thus, a conducting solution requires the presence of ions that can flow.
For instance:

• Molecular compounds like acetone do not typically conduct electricity because they do not dissociate into ions in solution.
• In contrast, ionic compounds, such as ammonium nitrate, dissociate into ions when dissolved in water, enabling the solution to conduct electricity proficiently.

So, the presence and ability of dissociation into ions is key to understanding a solution’s conductivity.

Ionization

Ionization is the process by which neutral molecules gain or lose electrons and form ions. This process is crucial in understanding whether a solution can conduct electricity. When a substance dissolves and ionizes, it produces ions that allow electrical currents to flow through the solution.

• Molecular compounds often do not ionize in water, as they usually consist of nonmetals that share electrons and do not break apart into ions.
• On the other hand, ionic compounds naturally ionize in solution because they are composed of cations and anions.

Ammonium nitrate is a perfect example of an ionic compound that ionizes completely in water, leading to excellent conductivity due to the release of \(\mathrm{NH}_4^+\) and \(\mathrm{NO}_3^-\) ions.

Molecular Compounds

Molecular compounds are composed of nonmetals held together by covalent bonds, where atoms share electrons. This strong internal bonding means they usually do not dissociate into ions when dissolved in water.
Consequently, solutions of molecular compounds, like acetone, typically do not conduct electricity because there aren't any ions present to carry charge. Some key points include:

• Molecular compounds do not break into simpler charged particles in solution.
• They might dissolve well in water, but without ionization, they do not facilitate electricity flow.

Understanding the behavior of molecular compounds when dissolved is crucial in predicting their effect on solution conductivity.

Ionic Compounds

Ionic compounds are made up of metals and nonmetals that transfer electrons, forming positive and negative ions. These compounds inherently ionize in aqueous solutions, providing the free ions required for conductivity.
When ammonium nitrate dissolves in water, it separates into \(\mathrm{NH}_4^+\) and \(\mathrm{NO}_3^-\), facilitating the flow of electric current. Here are some insights:

• Ionic compounds commonly dissociate into ions when they come into contact with polar solvents like water.
• This dissociation dramatically enhances the solution's ability to conduct electricity.

The complete ionization exemplified by ammonium nitrate underscores why ionic compounds are crucial in solutions requiring conductivity.