Problem 64 - Chemistry Principles and Practice

Question

Write an equation for each of the following reactions. (a) preparation of dinitrogen oxide (b) reaction of hydrazine with oxygen (c) reaction between \(\mathrm{P}_{4} \mathrm{O}_{10}\) and water

Step-by-Step Solution

Answer

(a) NH₄NO₃ → N₂O + 2H₂O; (b) N₂H₄ + O₂ → N₂ + 2H₂O; (c) P₄O₁₀ + 6H₂O → 4H₃PO₄.

Step 1: Understand the Reaction for Preparation of Dinitrogen Oxide

Dinitrogen oxide, also known as nitrous oxide, can be prepared by gently heating ammonium nitrate. The reaction decomposes the ammonium nitrate into dinitrogen oxide (N₂O) and water. The balanced chemical reaction can be written as:\[ \text{NH}_4\text{NO}_3 (s) \rightarrow \text{N}_2\text{O} (g) + 2\text{H}_2\text{O} (g) \]

Step 2: Write the Reaction of Hydrazine with Oxygen

Hydrazine (N₂H₄) reacts with oxygen to form nitrogen gas and water. To find the balanced chemical equation, equate the number of nitrogen, hydrogen, and oxygen atoms on each side. The balanced reaction is:\[ \text{N}_2\text{H}_4 (l) + \text{O}_2 (g) \rightarrow \text{N}_2 (g) + 2\text{H}_2\text{O} (g) \]

Step 3: Write the Reaction between P₄O₁₀ and Water

When phosphorus pentoxide (P₄O₁₀) reacts with water, it forms phosphoric acid. For every mole of P₄O₁₀, six moles of water are required to produce four moles of phosphoric acid. The reaction is:\[ \text{P}_4\text{O}_{10} (s) + 6\text{H}_2\text{O} (l) \rightarrow 4\text{H}_3\text{PO}_4 (aq) \]

Key Concepts

Balanced Chemical Equations

Balancing chemical equations is a crucial aspect of chemistry. It ensures the conservation of mass, meaning atoms are neither created nor destroyed in a chemical reaction. A balanced equation has the same number of each type of atom on both sides of the equation.
For example, in the preparation of dinitrogen oxide through the decomposition of ammonium nitrate:

• The equation is originally written as \(\text{NH}_4\text{NO}_3 \rightarrow \text{N}_2\text{O} + \text{H}_2\text{O}\).
• To balance it, we write \(\text{NH}_4\text{NO}_3 (s) \rightarrow \text{N}_2\text{O} (g) + 2\text{H}_2\text{O} (g)\).
• This equation shows each nitrogen, hydrogen, and oxygen atom is conserved.

Balancing equations requires practice, but with time, it'll become second nature, allowing you to focus on understanding the reactions themselves.

Reaction Stoichiometry

Stoichiometry is the part of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. Understanding this concept is essential to predict how much of a product could be produced from given reactants.
Take the reaction of hydrazine with oxygen:

• The balanced reaction is \(\text{N}_2\text{H}_4 (l) + \text{O}_2 (g) \rightarrow \text{N}_2 (g) + 2\text{H}_2\text{O} (g)\).
• This tells us that 1 mole of \(\text{N}_2\text{H}_4\) reacts with 1 mole of \(\text{O}_2\) to produce 1 mole of \(\text{N}_2\) and 2 moles of water.
• Reaction stoichiometry helps us calculate the exact quantities needed and produced in a reaction, ensuring efficient use of resources.

Mastering stoichiometry is a vital skill in chemistry, aiding in both laboratory and industrial applications.

Decomposition Reactions

A decomposition reaction occurs when one compound breaks down into two or more simpler substances. These reactions are often driven by heat, light, or electricity. They are a type of chemical reaction that changes complex molecules into simpler ones.
In the case of dinitrogen oxide production:

• Ammonium nitrate \((\text{NH}_4\text{NO}_3)\) decomposes upon heating.
• The decomposition reaction forms \(\text{N}_2\text{O}\) and \(\text{H}_2\text{O}\).
• This type of reaction highlights how heat can drive chemical change, breaking bonds in the original compound to form simpler molecules.

Decomposition reactions are common in various chemical processes, including the breakdown of organic material in nature.

Oxidation Reactions

Oxidation reactions involve the transfer of electrons, typically resulting in the increase in oxidation state of the substance involved. They are often paired with reduction reactions in redox processes.
Consider the reaction of hydrazine with oxygen:

• This can be seen as a type of oxidation reaction where hydrazine \((\text{N}_2\text{H}_4)\) is oxidized by \((\text{O}_2)\).
• In this context, oxygen acts as the oxidizing agent, receiving electrons from hydrazine.
• The products are nitrogen gas and water, where oxidation numbers change, reflecting electron transfer.

Understanding oxidation reactions is essential as they're fundamental in many natural processes, like cellular respiration and combustion.