Problem 28 - A Complete Resource Book in Chemistry for JEE Main

Question

On heating sodium metal in a current of dry ammonia, the compound formed is (a) sodium hydride (b) sodium amide (c) sodium azide (d) sodium nitride

Step-by-Step Solution

Answer

The compound formed is sodium amide (b).

Step 1: Understand the Reaction

We start by understanding the reaction between sodium metal (Na) and dry ammonia (NH₃). Generally, metals like sodium react with ammonia to form metal amides, releasing hydrogen as a byproduct. This knowledge guides us toward the type of reaction involved.

Step 2: Identify the Products

When sodium metal is heated in dry ammonia, the main product formed is sodium amide (\(\text{NaNH}_2\)), and hydrogen gas (\(\text{H}_2\)) is released. This is because the metal amide is a typical product when alkali metals react with ammonia.

Step 3: Verify the Answer

From the given options, we identify the compound formed through the reaction. Since sodium amide is expected when sodium reacts with ammonia, option (b) sodium amide matches our observation from Step 2.

Key Concepts

Sodium Metal Reactions

Sodium metal is known for its reactivity, especially reaction tendencies with nonmetals and certain compounds. One of the intriguing aspects of sodium reactions is its interaction with dry ammonia. When sodium metal is heated in a stream of dry ammonia, it reacts to form sodium amide. This process involves the release of hydrogen gas as a byproduct. Such reactions are driven by sodium's eager disposition to donate electrons and form ionic compounds. This characteristic makes sodium metallic reactions typically exothermic, releasing heat energy.

• Sodium (Na) readily loses one electron to achieve a stable noble gas configuration.
• This electron is captured by ammonia molecules, converting them into amide ions.
• The free hydrogen atoms then pair up to form hydrogen gas.

Understanding sodium reactions not only helps in predicting products but is also crucial in controlling reaction conditions and safety protocols in chemical industries.

Ammonia Reactions

Ammonia, a simple molecule consisting of one nitrogen and three hydrogen atoms (\(NH_3\)), plays a vital role in various chemical reactions. One such reaction is with metals, such as sodium. When ammonia reacts with alkali metals, it forms metal amides. In this specific context, sodium interacts with dry ammonia to produce sodium amide and hydrogen gas as seen in the equation:\[\text{2Na} + 2\text{NH}_3 \rightarrow \text{2NaNH}_2 + \text{H}_2\]

• Ammonia acts as a source of nitrogen in its reactions with metals.
• It serves both as a reactant and a medium for electron transfer in these reactions.
• Reactions with ammonia are often employed for synthesizing amides and nitrides.

Understanding ammonia's behavior in such reactions is fundamental in industries manufacturing fertilizers, explosives, and other nitrogen-related compounds.

Chemical Reaction Analysis

Analyzing chemical reactions involves breaking down the sequence of events and identifying the resulting products. Here, we focus on the reaction between sodium metal and ammonia to form sodium amide. In this reaction, sodium metal acts as the electron donor, while the ammonia molecules take on electron-acceptance roles. Analysis of such reactions uncovers several aspects:

• Reactants and Products: The primary reactants are sodium metal and dry ammonia, leading to the formation of sodium amide and hydrogen gas.
• Energy Flow: Reactions involving sodium tend to be exothermic, releasing heat due to breaking and forming of chemical bonds.
• Electron Transfer: Sodium donates electrons, which are essential in breaking the NH bonds within ammonia, facilitating product formation.

In chemical reaction analysis, understanding the roles of different reactants and how they interact provides insight into controlling and optimizing these reactions in practical applications.