Question

Which of the following occurs when crystals of iron$\left(\mathrm{II}\right)$ sulphate are heated?

• A. Irritating choking smell is formed.
• B. Smell of rotten egg is formed.
• C. No reaction takes place.
• D. Iron$\left(\mathrm{II}\right)$ salt and water are produced.

Answer 1

The correct option is A

Irritating choking smell is formed.

Option A

An irritating choking smell is formed.

Explanation of correct option:

• Decomposition reaction: Reaction in which reactant is broken down into two or more products in the presence of heat, light or electricity. $\mathrm{A}\to \mathrm{B}+\mathrm{C}$.
• Reaction:

$\underset{\mathrm{Sulphate}}{\underset{\mathrm{Iron}\left(\mathrm{II}\right)}{2{\mathrm{FeSO}}_4\left(\mathrm{s}\right)}}\underset{\mathrm{Oxide}}{\underset{\mathrm{Iron}\left(\mathrm{III}\right)}{\stackrel{∆}{\to }{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)}}+\underset{\mathrm{Dioxide}}{\underset{\mathrm{Sulphur}}{{\mathrm{SO}}_2\left(\mathrm{g}\right)}}+\underset{\mathrm{Trioxide}}{\underset{\mathrm{Sulphur}}{{\mathrm{SO}}_3\left(\mathrm{g}\right)}}$

• Here in the presence of heat decomposition is taking place so it is known as thermal decomposition.
• Iron(II) sulfate is decomposed into reddish-brown color iron(III) oxide and the evolution of colorless gases takes place which are ${\mathrm{SO}}_2$ and ${\mathrm{SO}}_3$ they have a choking and pungent odor.

So options B, C, and D are incorrect.

Thus, the correct answer is Option A Irritating choking smell is formed.