Chapter 8: Problem 105

When magnesium metal is burned in air, it forms two products \(A\) and \(B\). A reacts with water to form a basic solution. B reacts with water to form a similar solution as that of A plus a gas with a pungent odor. Identify \(A\) and \(B\) and write equations for the reactions.

Short Answer

Expert verified

Compound A is Magnesium Oxide and Compound B is Magnesium Nitride. The equations for the reactions are: \[2Mg + O_{2} \rightarrow 2MgO \], \[3Mg + N_{2} \rightarrow Mg_{3}N_{2}\], \[MgO + H_{2}O \rightarrow Mg(OH)_{2}\] and \[Mg_{3}N_{2} + 6H_{2}O \rightarrow 3Mg(OH)_{2} + 2NH_{3}\].

Step by step solution

Formation of Compound A and B

Magnesium burns in air to form magnesium oxide (compound A) and magnesium nitride (compound B). The balanced chemical equations of these reactions are as follows: \[2 Mg + O_{2} \rightarrow 2 MgO \] - Formation of Magnesium Oxide (A). \[3 Mg + N_{2} \rightarrow Mg_{3}N_{2} \] - Formation of Magnesium Nitride (B).

Reaction of Compound A with Water

The reaction of magnesium oxide (compound A) with water forms Magnesium Hydroxide which is a basic solution. The balanced chemical equation of this reaction is as follows: \[ MgO + H_{2}O \rightarrow Mg(OH)_{2} \] - Reaction of Magnesium Oxide (A) with Water.

Reaction of Compound B with Water

The reaction of magnesium nitride (compound B) with water forms Magnesium Hydroxide (which is the basic solution) and Ammonia (the gas with a pungent odor). The balanced chemical equation of this reaction is as follows: \[ Mg_{3}N_{2} + 6H_{2}O \rightarrow 3Mg(OH)_{2} + 2NH_{3}\] - Reaction of Magnesium Nitride (B) with Water.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Magnesium Oxide

Magnesium oxide is formed when magnesium metal reacts with oxygen during combustion. The reaction is highly exothermic, producing a bright white flame. The balanced chemical equation is:
\[2 Mg + O_{2} \rightarrow 2 MgO \]
Magnesium oxide is a white powdery substance that has a variety of uses, including as a refractory material due to its high melting point. When combined with water, magnesium oxide forms magnesium hydroxide, which is a basic solution, indicating that it can neutralize acids to form a salt and water.

Magnesium Nitride

When magnesium burns in air, apart from reacting with oxygen, it also reacts with nitrogen, which leads to the formation of magnesium nitride. This reaction can be depicted by the equation:
\[3 Mg + N_{2} \rightarrow Mg_{3}N_{2} \]
Magnesium nitride is less stable in the presence of water, and it will ultimately produce magnesium hydroxide and ammonia gas when water is added. The production of ammonia is evidenced by its characteristic sharp, pungent odor.

Magnesium Hydroxide

Magnesium hydroxide is formed when magnesium oxide or magnesium nitride reacts with water. It is poorly soluble in water, which leads to the formation of a suspension often referred to as 'milk of magnesia', used as an antacid or laxative. The formation from magnesium oxide is:
\[MgO + H_{2}O \rightarrow Mg(OH)_{2} \]
When magnesium hydroxide is formed, it creates a basic or alkaline environment, which can be proven by its ability to turn red litmus paper to blue.

Reaction with Water

Magnesium's reactions with water are not as immediate or dramatic as those of its alkali metal cousins, but with heat or when magnesium is in the form of a finely divided powder, it can react. Magnesium oxide reacts in a combination reaction to form magnesium hydroxide. Magnesium nitride undergoes a hydrolysis reaction, reacting with the water to produce magnesium hydroxide and ammonia gas. Both reactions eventually lead to the formation of a basic aqueous solution, indicating the alkaline nature of magnesium compounds when in water.

Basic Solution Chemistry

A basic solution results from the dissolution of a base in water. Magnesium hydroxide, which forms in the reactions mentioned, is a common base. When it is dissolved in water, it increases the concentration of hydroxide (\( OH^- \) ions in the solution, making it basic. The pH level of a basic solution is above 7. Basic solutions can be used to neutralize acids, resulting in a chemical reaction that produces water and a salt. This is a key concept in understanding the neutralization processes in chemistry.

Ammonia Production

During the reaction of magnesium nitride with water, ammonia is produced along with magnesium hydroxide. The chemical reaction is:
\[ Mg_{3}N_{2} + 6H_{2}O \rightarrow 3Mg(OH)_{2} + 2NH_{3} \]
Ammonia is a colorless gas known for its pungent smell. It has significant uses in fertilizers and cleaning products. Its production from magnesium nitride is an example of nitrogen fixation, which is an essential process for converting atmospheric nitrogen into a form usable by plants and animals.

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When magnesium metal is burned in air, it forms two products \(A\) and \(B\). A reacts with water to form a basic solution. B reacts with water to form a similar solution as that of A plus a gas with a pungent odor. Identify \(A\) and \(B\) and write equations for the reactions.

Short Answer

Step by step solution

Formation of Compound A and B

Reaction of Compound A with Water

Reaction of Compound B with Water

Key Concepts

Magnesium Oxide

Magnesium Nitride

Magnesium Hydroxide

Reaction with Water

Basic Solution Chemistry

Ammonia Production

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