Problem 32 - A Complete Resource Book in Chemistry for JEE Main

Question

Sodium nitrate decomposes above \(-800^{\circ} \mathrm{C}\) to give (a) \(\mathrm{N}_{2}\) (b) \(\mathrm{O}_{2}\) (c) \(\mathrm{NO}_{2}\) (d) \(\mathrm{Na}_{2} \mathrm{O}\)

Step-by-Step Solution

Answer

The gas produced is O₂.

Step 1: Understanding the Decomposition Reaction

Sodium nitrate ( abla_3 ext{NO}_3) decomposes on heating. It undergoes a thermal decomposition reaction where the compound breaks down into simpler substances, including a gas.

Step 2: Identifying Possible Products

The decomposition of sodium nitrate typically produces sodium nitrite ( abla ext{NO}_2) and oxygen gas ( ext{O}_2). Here, ext{O}_2 is a common gaseous product of decomposition involving nitrates.

Step 3: Balancing the Reaction Equation

The balanced chemical equation for the decomposition of sodium nitrate is: o ext{NaNO}_3 ightarrow ext{NaNO}_2 + frac{1}{2} ext{O}_2 This equation shows that the decomposition of sodium nitrate yields sodium nitrite and oxygen gas.

Step 4: Concluding the Products

From the balanced equation, it is clear that chlorine dioxide ( ext{O}_2) is released during the decomposition of sodium nitrate. Among the options given, ext{O}_2 matches our expected gaseous product.

Key Concepts

Sodium Nitrate

Sodium nitrate, often referred to by its chemical formula \( \text{NaNO}_3 \), is an inorganic compound frequently utilized in fertilizers due to its high nitrogen content. This white crystalline solid is highly soluble in water and is also known for supporting oxidation, which makes it useful in various chemical reactions. When exposed to high temperatures, sodium nitrate undergoes decomposition, a process where it breaks down into simpler compounds. Understanding the behavior of sodium nitrate at elevated temperatures is crucial for many industrial applications, including the manufacture of explosives and preservatives.

Chemical Reaction Balancing

Balancing chemical equations is essential for representing chemical reactions accurately. Each chemical reaction must obey the law of conservation of mass, meaning the mass of the reactants must equal the mass of the products. To balance a chemical equation, you ensure that the number of atoms for each element is the same on both sides of the equation. Let’s look at the specific example of sodium nitrate decomposing: \( 2 \text{NaNO}_3 \rightarrow 2 \text{NaNO}_2 + \text{O}_2 \).
In this reaction, we need to ensure that the number of sodium (Na), nitrogen (N), and oxygen (O) atoms are the same before and after the reaction. It involves adjusting the coefficients (the numbers in front of compounds) to equalize the number of each type of atom on both sides. This balanced equation represents the decomposition accurately, ensuring you account for all atoms involved.

Decomposition Reactions

Decomposition reactions occur when a single compound breaks down into two or more simpler products, often under the influence of heat. These reactions are crucial in many industrial and chemical processes. In the case of sodium nitrate, the decomposition occurs when heated beyond approximately \( 800^{\circ} \text{C} \), producing sodium nitrite \( \text{NaNO}_2 \) and oxygen gas \( \text{O}_2 \).
Decomposition reactions are generally endothermic, meaning they absorb energy in the form of heat. Understanding these reactions is essential because they are foundational in chemical engineering, agriculture, and the environment, as they can involve hazardous substances or produce useful by-products.

Oxides of Nitrogen

Oxides of nitrogen are compounds composed of nitrogen and oxygen in various ratios. These compounds exist in multiple forms, such as \( \text{NO}_2 \) (nitrogen dioxide) and \( \text{N}_2 \text{O} \) (nitrous oxide), each having distinct properties and uses. They are significant because they are involved in various environmental processes and commercial applications.
Understanding oxides of nitrogen is important because they are common emissions from combustion engines and can contribute to air pollution and the greenhouse effect. In the decomposition of sodium nitrate, though \( \text{NO}_2 \) is not a product, it's crucial to have knowledge about different nitrogen oxides as they illustrate the diversity and specific conditions of decomposition reactions.