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ICSE Class 10 Chemistry Question 9 of 13

Practical Work — Question 10

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Question

Question 10

Identify the substance 'R' based on the information given below :

The pale green solid 'R' turns reddish brown on heating. Its aqueous solution gives a white precipitate with barium chloride solution. The precipitate is insoluble in mineral acids.

Answer

The substance 'R' is Ferrous sulphate (FeSO4.7H2O). 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 →Δ\xrightarrow{\Delta} FeSO4 + 7H2O

2FeSO4 →Δ\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.