Question

FeSO$_4$ decomposes on heating into :

• A. 'Fe$_2$O$_3$'
• B. 'Fe$_2$O$_3$' \& 'SO$_2$'
• C. 'Fe$_2$O$_3$' \& 'SO$_3$'
• D. 'Fe$_2$O$_3$', 'SO$_2$' and 'SO$_3$'

Hint:

Thermal decomposition reactions often produce simpler compounds, sometimes involving changes in oxidation states. For sulfates of transition metals like iron, the products commonly include the metal oxide and oxides of sulfur.

Answer 1

The Correct Option is D

Step 1: Understand the decomposition of ferrous sulfate (FeSO$_4$).
Ferrous sulfate (FeSO$_4$) is a green crystalline solid that decomposes upon strong heating. This is a common thermal decomposition reaction in chemistry. Step 2: Write the balanced chemical equation for the decomposition.
When ferrous sulfate heptahydrate (FeSO$_4 \cdot 7\text{H}_2\text{O}$) is heated, it first loses its water of crystallization to form anhydrous ferrous sulfate. Upon further strong heating, anhydrous ferrous sulfate decomposes into ferric oxide, sulfur dioxide, and sulfur trioxide. The balanced chemical equation for the thermal decomposition of anhydrous ferrous sulfate is: $2\text{FeSO}_4 (\text{s}) \xrightarrow{\text{heat}} \text{Fe}_2\text{O}_3 (\text{s}) + \text{SO}_2 (\text{g}) + \text{SO}_3 (\text{g})$ Step 3: Identify the products of the decomposition.
From the balanced equation, the products are ferric oxide (Fe$_2$O$_3$), sulfur dioxide (SO$_2$), and sulfur trioxide (SO$_3$). Step 4: Compare the products with the given options.
(1) 'Fe$_2$O$_3$': This is only one of the products.
(2) 'Fe$_2$O$_3$' \& 'SO$_2$': This is missing SO$_3$.
(3) 'Fe$_2$O$_3$' \& 'SO$_3$': This is missing SO$_2$.
(4) 'Fe$_2$O$_3$', 'SO$_2$' and 'SO$_3$': This option correctly lists all the products.
(4) 'Fe$_2$O$_3$', 'SO$_2$' and 'SO$_3$'