Problem 129 - A Complete Resource Book in Chemistry for JEE Main

Question

Metal \(X\) on heating in nitrogen gas gives Y.Y on treatment with \(\mathrm{H}_{2} \mathrm{O}\) gives a colourless gas which when passed through \(\mathrm{CuSO}_{4}\) solution gives a blue colour. \(\mathrm{Y}\) is (a) \(\mathrm{MgO}\) (b) \(\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}\) (c) \(\mathrm{Mg}_{3} \mathrm{~N}_{2}\) (d) \(\mathrm{NH}_{3}\)

Step-by-Step Solution

Answer

Y is \( \text{Mg}_3\text{N}_2 \) (Option c).

Step 1: Identify the Reaction for Metal X and N2

When a metal, such as magnesium (Mg), is heated in nitrogen gas, it forms magnesium nitride, \[ \text{3Mg} + \text{N}_2 \rightarrow \text{Mg}_3\text{N}_2 \] Therefore, \( Y \) is most likely \( \text{Mg}_3\text{N}_2 \).

Step 2: Understand Reaction of Y with H2O

Magnesium nitride reacts with water to produce magnesium hydroxide and ammonia. The reaction is:\[ \text{Mg}_3\text{N}_2 + 6\text{H}_2\text{O} \rightarrow 3\text{Mg(OH)}_2 + 2\text{NH}_3 \]The reaction produces ammonia gas, which is colorless.

Step 3: Connect to CuSO4 Interaction

When this ammonia gas is passed through a \( \text{CuSO}_4 \) solution, it forms a complex that gives a blue color.The formation of this complex can be described as:\[ \text{CuSO}_4 + 4\text{NH}_3 + \text{H}_2\text{O} \rightarrow \text{[Cu(NH}_3\text{)}_4]\text{SO}_4 + \text{H}_2\text{O} \]Thus, the color change to blue is due to the interaction of \( \text{NH}_3 \) with \( \text{CuSO}_4 \).

Step 4: Conclusion on Y

From the above reactions, we can confirm that \( \text{Y} \) is \( \text{Mg}_3\text{N}_2 \) because it produces \( \text{NH}_3 \) when reacted with water, which then interacts with \( \text{CuSO}_4 \) to give a blue color.

Key Concepts

Metal-Nitrogen Reactions

In the fascinating realm of inorganic chemistry, metal-nitrogen reactions often play crucial roles in synthesizing various important compounds. One significant reaction involves the interaction of a metal with nitrogen gas. When a metal, like magnesium, is heated in the presence of nitrogen, it readily forms a metal nitride. For magnesium, this reaction works as follows: - Magnesium (Mg) combines with nitrogen gas ( 2) - The product of this reaction is magnesium nitride, This type of reaction is fundamental in the formation of nitrides, which are compounds containing nitrogen bonded to a less electronegative element. Such reactions are significant in material science and industrial chemistry.

Magnesium Nitride

Magnesium nitride is a compound composed of magnesium and nitrogen, with the chemical formula This yellowish solid is typically produced when magnesium is sufficiently heated in a stream of nitrogen gas. The importance of magnesium nitride lies in its ability to further react with water. This property not only showcases its versatility but also underlines its utility in various chemical processes. When equation: This reaction produces magnesium hydroxide and ammonia gas. It's the release of ammonia that connects further with subsequent reactions, making magnesium nitride an intriguing compound to study.

Ammonia Formation from Nitride

The formation of ammonia from magnesium nitride is a captivating process that highlights the utility of nitrides. - As magnesium nitride reacts with water, it decomposes to form magnesium hydroxide and releases ammonia gas This phenomenon is not just of academic interest; ammonia itself is a colorless gas with significant industrial importance. It is widely used in fertilizers and is a critical reactant in various chemical syntheses. In the context of our exercise, the release of ammonia serves as a precursor to another reaction involving copper sulfate.

Copper Ammonia Complex

When ammonia, produced from the reaction of magnesium nitride with water, interacts with a copper sulfate solution, a unique color change occurs. This change is due to the formation of a copper ammonia complex. - Copper ions readily react with ammonia - The reaction creates This process is not only visually striking due to the vivid blue color of the complex but also valuable in understanding the nature of coordination compounds. Copper ammonia complexes are essential in both chemical analysis and various applications including catalysis and electroplating. The blue color serves as an indicator of the presence of molecular interactions between ammonia and copper ions, making it a classic demonstration in chemistry experiments.