Problem 1 - A Complete Resource Book in Chemistry for JEE Main

Question

When \(\mathrm{NH}_{4} \mathrm{Cl}\) is warmed with \(\mathrm{NaOH}\) in a test tube it is a case of (a) Open system (b) Closed system (c) Isolated system (d) Both a, c

Step-by-Step Solution

Answer

It is an open system.

Step 1: Understanding the Reaction

When ammonium chloride (\mathrm{NH}_{4} \mathrm{Cl}) reacts with sodium hydroxide (\mathrm{NaOH}), ammonia gas (\mathrm{NH}_{3}), water (\mathrm{H}_{2}\mathrm{O}), and sodium chloride (\mathrm{NaCl}) are produced. The reaction can be written as:\[\mathrm{NH}_{4} \mathrm{Cl(s)} + \mathrm{NaOH(aq)} \rightarrow \mathrm{NH}_{3(g)} + \mathrm{H}_{2} \mathrm{O(l)} + \mathrm{NaCl(aq)}\]

Key Concepts

Ammonium Chloride

Ammonium chloride is a white crystalline salt commonly used in various applications such as fertilizers, pharmaceuticals, and in the chemical industry. When

• exposed to air, it does not absorb water or become sticky, which makes it easy to handle.
• It is very soluble in water, where it dissolves to form a slightly acidic solution.

One of the significant characteristics of ammonium chloride is its ability to decompose into ammonia gas and hydrogen chloride gas when heated. This feature is particularly useful in laboratory settings, such as displayed in our chemical reaction with sodium hydroxide. To sum up, understanding ammonium chloride's basic properties and behavior, especially its reaction with sodium hydroxide, lays the groundwork for comprehending the formation of ammonia gas.

Sodium Hydroxide

Sodium hydroxide, commonly known as lye or caustic soda, is a strong base renowned for its use in soap-making and chemical production.

• It readily dissolves in water, producing significant heat, and forms a highly alkaline solution.
• Sodium hydroxide is very corrosive and can cause severe skin burns, making it important to handle with care.

In the reaction with ammonium chloride, sodium hydroxide acts to liberate ammonia gas. This process involves the transfer of an

• OH⁻ ion from the NaOH to the ammonium ion, resulting in the release of ammonia gas.

This reaction highlights sodium hydroxide's role as a base that pulls the components apart, allowing the two chemical substances to interact and produce new compounds, such as ammonia gas and water.

Ammonia Gas

Ammonia gas is a colorless gas with a distinct, pungent smell. It is lighter than air and dissolves readily in water, forming a solution known as ammonium hydroxide. Ammonia is produced in various industrial and natural processes, but in this particular reaction, it is generated through the interaction of

• ammonium chloride and sodium hydroxide.

Upon heating (

as seen in the exercise), the ammonium ion ( NH₄⁺) from ammonium chloride is converted to ammonia gas ( NH₃).

• Ammonia has wide-ranging uses from agricultural fertilizers to household cleaners.
• Its chemical properties make it a versatile tool in industrial applications, but it must be handled with care due to its corrosive nature.

Thus, the role of ammonia gas in this reaction not only demonstrates its formation but also highlights the practical understanding of how common reactions proceed involving ammonium compounds.