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. Y is: (a) \(\mathrm{MgO}\) (b) \(\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}\) (c) \(\mathrm{Mg}_{3} \mathrm{~N}_{2}\) (d) \(\mathrm{NH}_{3}\)

Short answer

The compound Y is \( \text{Mg}_3\text{N}_2 \).

Step-by-step solution

Identify the chemical reaction

When metal X (which is magnesium, \( \text{Mg} \)) is heated in the presence of nitrogen gas \( \text{N}_2 \), it forms a compound Y. The reaction is \( 3\text{Mg} + \text{N}_2 \rightarrow \text{Mg}_3\text{N}_2 \). This shows that compound Y is magnesium nitride \( \text{Mg}_3\text{N}_2 \).

Reaction of Y with H2O

When magnesium nitride \( \text{Mg}_3\text{N}_2 \) reacts with water \( \text{H}_2\text{O} \), it forms magnesium hydroxide \( \text{Mg(OH)}_2 \) and releases ammonia gas \( \text{NH}_3 \). The equation for this reaction is \( \text{Mg}_3\text{N}_2 + 6\text{H}_2\text{O} \rightarrow 3\text{Mg(OH)}_2 + 2\text{NH}_3 \).

Passing the gas through CuSO4 solution

The ammonia gas \( \text{NH}_3 \) is a colorless gas. When this gas is passed through a copper sulfate \( \text{CuSO}_4 \) solution, it forms a deep blue complex \( \text{[Cu(NH}_3)_4]^{2+} \), which indicates the presence of ammonia.

Determine Y

From the reactions and observations, we determined that Y is \( \text{Mg}_3\text{N}_2 \) because it releases ammonia gas when treated with water, which reacts with \( \text{CuSO}_4 \) to form a blue color.

Key concepts

Chemical Reactions

Chemical reactions are processes where reactants transform into products, often involving a change in energy and the breaking and forming of bonds. In the given exercise, the reaction starts with magnesium and nitrogen gas. For such a reaction to occur, energy in the form of heat is needed to break the bonds of the reactants and allow them to form new compounds.

This particular reaction is a synthesis reaction, in which the metal magnesium combines with nitrogen gas to form magnesium nitride.

• Synthesis reactions involve elements or simpler compounds combining to form a more complex molecule.
• These reactions commonly occur with the input of energy, like heat or light.

Recognizing chemical reactions and understanding how reactants transform can help predict the products of the reactions.

Compound Formation

Compound formation is the structural result of chemical reactions, involving the combination of two or more different elements. In this context, magnesium nitride is formed when magnesium combines with nitrogen.

• The chemical formula for magnesium nitride is \( \text{Mg}_3\text{N}_2 \).
• This compound is created through a direct combination reaction between metallic magnesium and nitrogen gas.

The reaction can be balanced as follows:\[3\text{Mg} + \text{N}_2 \rightarrow \text{Mg}_3\text{N}_2\]This synthesize results in a compound having distinct properties from the reactants, demonstrating the transformative nature of chemical processes.

Ammonia Gas

Ammonia gas, \( \text{NH}_3 \), is a crucial compound in many chemical reactions. It is a colorless gas with a distinct, pungent smell, commonly produced in nature by the decay of organic materials.

• In this exercise, ammonia gas is released when magnesium nitride reacts with water.
• The balanced chemical equation illustrating this reaction is:\[\text{Mg}_3\text{N}_2 + 6\text{H}_2\text{O} \rightarrow 3\text{Mg(OH)}_2 + 2\text{NH}_3\]

Ammonia's interaction with the copper sulfate solution, forming a deep blue color, highlights its role in chemical detection and reactions. This property is used to confirm the presence of ammonia in solutions.

Magnesium Nitride

Magnesium nitride, \( \text{Mg}_3\text{N}_2 \), is a compound formed by magnesium and nitrogen through a chemical reaction called a synthesis reaction. This compound is crucial in the cycle of the reaction described in the problem. It showcases several important chemical principles.

• Formation Reaction: \( 3\text{Mg} + \text{N}_2 \rightarrow \text{Mg}_3\text{N}_2 \).
• Reactivity with Water: It reacts with water to produce magnesium hydroxide and ammonia gas.

The reactions highlight the ease with which magnesium, a reactive metal, forms compounds with nonmetals like nitrogen, further demonstrating how metal nitrides often act as intermediates in various chemical processes.