Question

2 g of ferrous sulphate crystals are heated in a boiling tube.
(i) State the colour of ferrous sulphate crystals both before heating and after heating.
(ii) Name the gases produced during heating.
(iii) Write the chemical equation for the reaction.


CBSE Class X Science SA 2 (3 Marks)

Answer 1

2 g of ferrous sulphate crystals are heated in a boiling tube then  we observe that :
1 Ferrous sulphate crystals contains 2 water moelcules.
On heating it looses water molecules and becomes anhydrous ferrous sulphate .
2. Colour changes from  light green to white . Ferrous sulphate crystals  which are in green colour decomposes  to give Ferric oxide , sulphur dioxide and sulphur trioxide gas.
3. On further heating  FeSO4 anhydrous changes to dark brown solid ..

4. The gas emitted has the characteristics smell of sulphur.

Chemical reaction :.
2FeSO4 (S) -------------->Fe2O3 (S) +SO2(g) +SO3 (g)
Anhydrous                  Ferric oxide
Ferrous sulphate

Answer 2

Ferrous sulphate is blue-green in colour. On being heated, it loses water of crystallisation and the anhydrous ferrous sulphate further decomposes to ferric oxide, sulphur dioxide and sulphur trioxide. Ferric oxide is reddish brown in colour. This is an example of decomposition reaction. Following is the equation for the reaction
2FeSo4----------> Fe2O3+So2+SO3
 
So the colour of the salt befor heating is blue-green and after heating is reddish brown.