Understanding the Thermal Decomposition of FeSO₄

When solid Iron(II) sulfate (FeSO₄) is heated strongly, it undergoes thermal decomposition. This process breaks down the compound into simpler substances upon receiving heat energy. The decomposition of FeSO₄ is a classic example of a redox reaction and involves the formation of solid and gaseous products.

Chemical Reaction Upon Heating FeSO₄

The thermal decomposition of anhydrous FeSO₄ can be represented by the following balanced chemical equation:

$$2\text{FeSO}_4\text{(s)} \xrightarrow{\Delta} \text{Fe}_2\text{O}_3\text{(s)} + \text{SO}_2\text{(g)} + \text{SO}_3\text{(g)}$$

In this reaction:

• $\text{FeSO}_4$ is the reactant, a solid.
• The triangle symbol ($\Delta$) indicates heating.
• $\text{Fe}_2\text{O}_3$ (Iron(III) oxide) is a solid product.
• $\text{SO}_2$ (Sulfur dioxide) is a gaseous product.
• $\text{SO}_3$ (Sulfur trioxide) is also a gaseous product.

Therefore, upon heating $\text{FeSO}_4$, the gases obtained are Sulfur dioxide ($\text{SO}_2$) and Sulfur trioxide ($\text{SO}_3$).

Analysis of the Options

Let's examine the given options in the context of the thermal decomposition of $\text{FeSO}_4$:

• Option 1: Both $\text{SO}_2$ and $\text{SO}_3$ - As seen from the chemical equation, both Sulfur dioxide ($\text{SO}_2$) and Sulfur trioxide ($\text{SO}_3$) are produced as gases when $\text{FeSO}_4$ is heated. This aligns with the decomposition reaction.
• Option 2: $\text{H}_2\text{S}$ - Hydrogen sulfide ($\text{H}_2\text{S}$) is not a product of the thermal decomposition of $\text{FeSO}_4$. $\text{H}_2\text{S}$ is typically formed in reactions involving sulfides or reduction of sulfates under specific conditions, neither of which occurs in the simple heating of $\text{FeSO}_4$.
• Option 3: $\text{SO}_2$ - While $\text{SO}_2$ is one of the gaseous products, it is not the only one. The decomposition of $\text{FeSO}_4$ simultaneously produces $\text{SO}_3$.
• Option 4: $\text{SO}_3$ - Similarly, while $\text{SO}_3$ is one of the gaseous products, it is not the only one. The decomposition of $\text{FeSO}_4$ simultaneously produces $\text{SO}_2$.

Based on the balanced chemical equation and the nature of the products, the gases obtained on heating $\text{FeSO}_4$ are both $\text{SO}_2$ and $\text{SO}_3$.

Summary of FeSO₄ Decomposition Products

This table clearly shows that Sulfur dioxide ($\text{SO}_2$) and Sulfur trioxide ($\text{SO}_3$) are the gaseous products formed during the thermal decomposition of Iron(II) sulfate ($\text{FeSO}_4$).

Revision Table: Key Concepts

Additional Information: Thermal Decomposition Reactions

Thermal decomposition is a common type of chemical reaction, particularly for salts and oxides. Many compounds decompose upon heating to produce simpler substances. The products often depend on the specific compound and the temperature reached during heating.

Examples include:

• Decomposition of Calcium carbonate ($\text{CaCO}_3$): $\text{CaCO}_3\text{(s)} \xrightarrow{\Delta} \text{CaO}\text{(s)} + \text{CO}_2\text{(g)}$. This produces Calcium oxide and Carbon dioxide gas.
• Decomposition of Zinc carbonate ($\text{ZnCO}_3$): $\text{ZnCO}_3\text{(s)} \xrightarrow{\Delta} \text{ZnO}\text{(s)} + \text{CO}_2\text{(g)}$. This produces Zinc oxide and Carbon dioxide gas.
• Decomposition of Copper(II) nitrate ($\text{Cu(NO}_3)_2$): $2\text{Cu(NO}_3)_2\text{(s)} \xrightarrow{\Delta} 2\text{CuO}\text{(s)} + 4\text{NO}_2\text{(g)} + \text{O}_2\text{(g)}$. This produces Copper(II) oxide, Nitrogen dioxide gas, and Oxygen gas.

Understanding these decomposition reactions is crucial in studying chemistry, especially inorganic chemistry and chemical kinetics.