Problem 22 - Chemistry in 30 days

Question

Ferrous sulphate on heating gives (a) \(\mathrm{SO}_{2}\) and \(\mathrm{SO}_{3}\) (b) \(\mathrm{SO}_{2}\) only (c) \(\mathrm{SO}_{3}\) only (d) \(\mathrm{SO}_{2}\) and \(\mathrm{O}_{2}\)

Step-by-Step Solution

Answer

Option (a): \\( ext{SO}_2 \\) and \\( ext{SO}_3 \\).

Step 1: Identify the chemical compound

Ferrous sulphate is chemically represented as \( ext{FeSO}_4 \) and it is a common iron salt.

Step 2: Understand the decomposition process

When \( ext{FeSO}_4\) is heated, it undergoes a decomposition reaction where it breaks down into simpler substances.

Step 3: Write the decomposition reaction equation

The decomposition reaction of ferrous sulphate on heating is: \[ 2 ext{FeSO}_4 ightarrow ext{Fe}_2 ext{O}_3 + ext{SO}_2 + ext{SO}_3 \].

Step 4: Identify the gaseous products

From the reaction equation: \(2 ext{FeSO}_4 ightarrow ext{Fe}_2 ext{O}_3 + ext{SO}_2 + ext{SO}_3\), you can see that \( ext{SO}_2 \) and \( ext{SO}_3 \) are both produced as gaseous products.

Step 5: Select the correct answer from the options

Considering the gaseous products identified, the correct choice provided in the exercise is option (a) \( ext{SO}_2 \) and \( ext{SO}_3 \).

Key Concepts

Ferrous Sulphate

Ferrous sulphate, known reformally as iron(II) sulfate, is a blue-green crystalline compound represented by the chemical formula \( \text{FeSO}_4 \). Often found with water molecules attached, such as in its common hydrated form, \( \text{FeSO}_4\cdot7\text{H}_2\text{O} \), it serves various roles. Primarily, it's used in agriculture as a soil amendment to correct iron chlorosis in plants. Additionally, it's a component in some pharmaceutical products, mainly as an iron supplement to treat anemia.

• Appearance: Blue-green crystals in hydrated form
• Uses: Iron supplements, soil amendment
• Chemical Formula: \( \text{FeSO}_4 \)

Understanding ferrous sulphate is key in recognizing its transformation during thermal decomposition.

Chemical Equation Balancing

Chemical equation balancing is crucial for representing reactions accurately. It ensures the law of conservation of mass is followed by having equal amounts of each element on both sides of the equation. This principle applies to the reaction of ferrous sulphate's thermal decomposition. When balanced, the equation reads:
\[ 2 \text{FeSO}_4 \rightarrow \text{Fe}_2\text{O}_3 + \text{SO}_2 + \text{SO}_3 \].
Here’s why this equation is balanced:

• Iron atoms: Two \( \text{Fe} \) on both sides of the equation.
• Sulfur atoms: Two \( \text{S} \) on both sides combined as \( \text{SO}_2 \) and \( \text{SO}_3 \).
• Oxygen atoms: Eight on each side, from \( \text{FeSO}_4 \), \( \text{Fe}_2\text{O}_3 \), and the gaseous products.

Balancing ensures that students comprehensively understand the stoichiometry in decomposition reactions.

Gaseous Products

During the thermal decomposition of ferrous sulphate, two important gaseous products are formed: sulfur dioxide \( \text{SO}_2 \) and sulfur trioxide \( \text{SO}_3 \). These gases contribute significantly to various chemical processes and natural phenomena, like atmospheric reactions that may form sulfuric acid, a part of acid rain.

• \( \text{SO}_2 \): Known for its pungent smell, it's a precursor to sulfate particles.
• \( \text{SO}_3 \): Reacts with water vapor forming \( \text{H}_2\text{SO}_4 \), influencing environmental conditions.

Understanding gaseous products is essential to grasp the overall implications of chemical reactions in the environment.

Thermal Decomposition

Thermal decomposition is a type of chemical reaction where a compound breaks down into simpler substances when heated. In the case of ferrous sulphate, heating leads to the breakdown of \( \text{FeSO}_4 \) into iron(III) oxide (\( \text{Fe}_2\text{O}_3 \)) and the gaseous products \( \text{SO}_2 \) and \( \text{SO}_3 \).
Key aspects of thermal decomposition:

• Requires Heat: Reaction initiated and driven by heat supply.
• Endothermic: Absorbs heat energy during decomposition.
• Produces New Substances: Results in derivatives like \( \text{Fe}_2\text{O}_3 \).

These aspects confirm why thermal decomposition reactions are significant in industrial applications and environmental science.