Question

What is the colour of ferrous sulphate crystals? How does this colour change after heating?

Answer 1

Hint: In order to this question, to know the colour of sulphate crystals, we should go through the mechanism of ferrous sulphate with the reaction. And then we will discuss how the colour of ferrous sulphate crystals change after heating.

Complete answer:
The ferrous sulphate crystals are light green. Ferrous sulphate is also obtained as a by-product in the manufacture of titanium pigment and copper sulphate. The colour changes from light green to white colour. On further heating white substance turns into dark brown solid.
\[2FeS{O_4} \to F{e_2}S{O_3} + S{O_3} + S{O_2}\]
Ferrous sulphate crystals contain water of crystallisation \[\left( {FeS{O_4}.7{H_2}O} \right)\] . On heating, ferrous sulphate crystals lose water. So their colour changes from light green to white due to the formation of anhydrous ferrous sulphate \[(FeS{O_4})\] . When ferrous sulphate is heated, it gives ferric oxide, sulphur dioxide and sulphur trioxide.

Note:
Ferrous sulphate crystals contain water molecules as water of crystallization - \[\left( {FeS{O_4}.7{H_2}O} \right)\] . On heating, ferrous sulphate crystals lose water and anhydrous ferrous sulphate \[\left( {FeS{O_4}} \right)\] is formed. Due to this, it's colour changes from light green to white.