Question

\(\mathrm{NH}_{4} \mathrm{Cl}\) solution is: (a) Neutral (b) Acidic (c) Basic (d) Amphoteric

Short answer

The \(\mathrm{NH}_4\mathrm{Cl}\) solution is acidic (b).

Step-by-step solution

Identify the Ions Formed in Solution

When ammonium chloride, \(\mathrm{NH}_4\mathrm{Cl}\), is dissolved in water, it dissociates into ammonium ions \(\mathrm{NH}_4^+\) and chloride ions \(\mathrm{Cl}^-\).

Determine the Nature of Individual Ions

The chloride ion \(\mathrm{Cl}^-\) is the conjugate base of hydrochloric acid \(\mathrm{HCl}\), which is a strong acid, so \(\mathrm{Cl}^-\) is neutral in solution. The ammonium ion \(\mathrm{NH}_4^+\), on the other hand, is a conjugate acid of ammonia \(\mathrm{NH}_3\), making it acidic in solution.

Assess the Overall Solution's Nature

Since \(\mathrm{NH}_4^+\) is acidic and \(\mathrm{Cl}^-\) is neutral, the overall effect of the ions from the dissociation of ammonium chloride results in an acidic solution.

Key concepts

Ammonium Chloride

Ammonium chloride is a white crystalline salt that can be easily dissolved in water. When you look at the chemical formula of ammonium chloride, \(NH_4Cl\), you will notice it comprises two types of ions, ammonium \(NH_4^+\) and chloride \(Cl^-\). These ions are responsible for different properties when in a solution.
Ammonium chloride is commonly used in laboratories and industry for applications ranging from fertilizers to batteries and even cough medicine. Its utility is largely derived from its ability to dissociate into its respective ions in aqueous solutions.
Understanding how ammonium chloride behaves when dissolved in water involves looking at the interaction between these ions, which brings us to the concept of solution chemistry.

Solution Chemistry

Solution chemistry focuses on the processes that occur when a solute dissolves in a solvent, like when ammonium chloride is mixed with water. The solute, ammonium chloride, separates into individual ions: ammonium \(NH_4^+\) and chloride \(Cl^-\). This separation is known as dissociation and is crucial for the behavior of solutions in chemistry.
In this particular case, because the ammonium ion acts as a weak acid while the chloride ion is neutral, the water solution becomes acidic. This is due to the ability of the ammonium ion to donate a hydrogen ion \(H^+\) in water, which increases the hydrogen ion concentration, resulting in a lower pH level.

• Solvent: The substance that dissolves the solute, which is water in this scenario.
• Solute: The substance being dissolved, which is the ammonium chloride.
• Dissociation: The process by which a compound breaks down into its respective ions in solution.
• Overall pH: Indicates the acidity or alkalinity of the solution after dissolution.

Knowing these fundamentals helps in predicting the nature of the solution formed by various compounds in water.

Dissociation in Water

When ammonium chloride is introduced into water, it undergoes a process called dissociation, where the compound breaks into its constituent ions. In this case, \(NH_4Cl\) dissociates into ammonium ions \(NH_4^+\) and chloride ions \(Cl^-\). This dissociation is crucial because it determines the chemical behavior and properties of the solution.
Once dissolved, the ammonium ion can act as a weak acid by donating hydrogen ions \(H^+\) to the solution. This donation affects the pH, contributing to the overall acidity of the solution. Conversely, the chloride ion, being the conjugate base of a strong acid, hydrochloric acid, does not significantly affect the acidity.

• Dissociation Equilibrium: The stage where the rate of dissociation of ammonium chloride equals the rate of recombination to form the solid salt in the solution.
• pH Impact: More \(H^+\) ions in the solution lower the pH, indicating acidity.

This basic understanding of dissociation in water helps to explain why certain salts, when dissolved, affect the solution's acidity, leading to important implications in chemistry and various real-world applications.