Question

On heating green coloured ferrous sulphate crystals, a reddish brown solid is left out and the smell of a gas having the odour of burning sulphur is obtained. Identify the type of reaction involved.

• A. Combustion
• B. Thermal Decomposition
• C. Electrolytic Decomposition
• D. Displacement

Answer 1

The correct option is B Thermal Decomposition

$2FeS{O}_4\to F{e}_2{O}_3+S{O}_2+S{O}_3$

This is a thermal decomposition reaction.

On heating, ferrous sulphate crystals lose water and anhydrous ferrous sulphate is formed. Hence the colour changes.

On further heating anhydrous ferrous sulphate decomposes to form ferric oxide, sulphur dioxide and sulphur trioxide.$S{O}_2$ gives the smell of burning sulphur.