Question 2(2009)Identity the substance 'R' based on the information given below : The pale green solid 'R' turns reddish brown on heating. It's aqueous solution gives a white precipitate with barium chloride solution. The precipitate is insoluble in mineral acids.

Question

Accepted Answer

The substance 'R' is Ferrous sulphate (FeSO₄.7H₂O).

Reason

When heated strongly, the hydrous pale green ferrous sulphate (FeSO₄.7H₂O), loses it's water of crystallization and decomposes to form brown ferric oxide Fe₂O₃ along with sulphur dioxide (SO₂) and sulphur trioxide (SO₃).

FeSO₄.7H₂O $\xrightarrow{\Delta}$ FeSO₄ + 7H₂O

2FeSO₄ $\xrightarrow{\Delta}$ Fe₂O₃ + SO₂ + SO₃

Ferrous sulphate on reaction with barium chloride soln., forms a white ppt. of barium sulphate (BaSO₄) which is insoluble in mineral acids.

Practical Chemistry — Question 9

Question 2(2009)