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

Short answer

The compound formed is sodium amide (b).

Step-by-step solution

Analyze the Reactants

We are given sodium metal (Na) and dry ammonia (NH₃) as reactants. Our goal is to understand the possible reaction between these substances.

Predict the Possible Reaction Products

When sodium metal reacts with ammonia, an understanding of the chemical behavior of both is necessary. Sodium is an alkali metal known to form ionic compounds, and it can react with the N-H bond of ammonia.

Identify the Reaction Mechanism

In the presence of sodium metal, ammonia can decompose, releasing hydrogen gas and forming the sodium amide compound. Sodium amide is created when sodium interacts with ammonia to release hydrogen: \(2 \text{Na} + 2 \text{NH}_3 \rightarrow 2 \text{NaNH}_2 + \text{H}_2\).

Determine the Correct Product

After analyzing the reaction, it is evident that sodium amide (NaNH₂) is formed in this reaction. Hence, the correct answer is sodium amide.

Key concepts

Reaction of Sodium with Ammonia

When sodium metal comes into contact with dry ammonia, an interesting chemical reaction occurs. This process is fundamental in understanding basic chemistry concepts like ionic bonding and decomposition. Initially, sodium as an alkali metal exhibits a strong tendency to lose its valence electron, such a reactive behavior sets the stage for interactions with ammonia. Ammonia, a compound with distinct nitrogen-hydrogen bonds, reacts with sodium. The reaction can be represented through the equation: \[2 \text{Na} + 2 \text{NH}_3 \rightarrow 2 \text{NaNH}_2 + \text{H}_2\] In this reaction, sodium reacts with ammonia to yield sodium amide and hydrogen gas. This clearly shows sodium breaking the N-H bonds in ammonia and forming a new compound, sodium amide, alongside hydrogen release. Understanding this fundamental chemical interaction highlights sodium's propensity to form ionic compounds.

Ionic Compounds of Alkali Metals

Alkali metals, such as sodium, are known for their strong tendency to form ionic compounds. These metals have a single valence electron, which they readily lose, resulting in a positively charged ion or cation. This is particularly significant in the formation of sodium amide. When sodium reacts with ammonia, it forms an ionic compound where sodium donates an electron to one of the hydrogen atoms in ammonia, leading to the release of hydrogen gas and the creation of sodium amide. This process highlights a key property of alkali metals: their ability to form stable ionic bonds with non-metals by transferring electrons.

• Cation Formation: Sodium loses an electron to become \( \text{Na}^+ \).
• Anion Formation: The resulting ions combine to create \( \text{NaNH}_2 \) — sodium amide.

Sodium's affinity for losing its electron and forming ionic bonds makes it a representative example of alkali ionic compounds.

Decomposition of Ammonia

Decomposition involves breaking down compounds into simpler substances. In the reaction between sodium and ammonia, ammonia decomposes partially. Here, sodium is responsible for breaking the N-H bonds in ammonia. This decomposition leads to the formation of new products: sodium amide and hydrogen gas. The concept of decomposition not only describes breaking the compound into parts but also emphasizes on chemical transformations. For example, in the sodium-ammonia reaction, the strong ionic nature of sodium forces ammonia's molecular structure to split, emphasizing the vigorous interaction, even under typical conditions. This reaction is a classic demonstration of how a simple heating process can lead to the decomposition and transformation of chemical compounds.

Chemical Reaction Mechanisms

Chemical reaction mechanisms provide a detailed step-by-step description of the re-arrangements of atoms or ions that occur during reactions. In the reaction of sodium with ammonia, understanding the mechanism is key to comprehending the overall process. Initially, metallic sodium, with its high reactivity, interacts with ammonia molecules. This interaction causes the N-H bond in ammonia to break, facilitating the release of hydrogen gas. Sodium then binds to the nitrogen to form sodium amide. Breaking down this mechanism enhances the understanding of how different functional groups interact and the roles played by each reactant.

• Initiation: Sodium atoms donate an electron to initiate the reaction.
• Breaking Bonds: N-H bonds in ammonia break, releasing hydrogen gas.
• New Compound Formation: Sodium binds with nitrogen forming sodium amide.

Comprehending such mechanisms allows insights into the fundamental interactions driving chemical transformations.