Question

You are given with following material:

Ferrous sulphate crystals

Identify the type of chemical reaction taking place when:

On heating, green ferrous sulphate crystals, reddish-brown solid is left and gas having smell of burning sulphur is noticed.

Answer 1

Dehydration reaction:

A chemical reaction in which a substance loses water molecules under suitable conditions.

Decomposition reaction:

1. A chemical reaction in which one component decomposes to form two or more single substances.
2. The given reaction of heating of green ferrous sulphate$\left({\mathrm{FeSO}}_4\right)$ crystals, a reddish-brown Ferric oxide$\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ solid is produced and the gases namely Sulphur dioxide$\left({\mathrm{SO}}_2\right)$ and Sulphur trioxide$\left({\mathrm{SO}}_3\right)$ formed has the smell of burning Silver.
3. First, the Ferrous sulphate losses its water molecule due to heating.
4. Hence, it is an example of a Dehydration reaction.

The reaction is written as ${\mathrm{FeSO}}_4.7{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)\stackrel{\mathrm{heat}}{\to }{\mathrm{FeSO}}_4\left(\mathrm{s}\right)+7{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

On further heating ferrous sulphate undergoes a Decomposition reaction.

$2{\mathrm{FeSO}}_4\left(\mathrm{s}\right)\stackrel{\mathrm{heat}}{\to }{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{SO}}_3\left(\mathrm{g}\right)$