Question

II) Take about 2 g ferrous sulphate crystals in a dry boiling tube. Heat the boiling tube over the flame of a burner or spirit lamp. In this reaction you can observe that a single
reactant breaks down to give simpler products. This is a decomposition reaction.
Ferrous sulphate crystals (FeSO4, 7H2O) lose water when heated and the colour of the crystals change. It then decomposes to ferric oxide (Fe2O3), sulphur dioxide (SO2)
and sulphur trioxide (SO3). Ferric oxide is a solid, while SO2 and SO3 are gases.

Answer 1

Answer:

The answer to the above questions are:

D

A

B

Answer 2

In the given experiment, when ferrous sulphate is heated it decomposes -

(1) The evolution of water vapor, change in color, and smell of sulphur is observed during the experiment. (OPTION D)

(2) The color of the solution changes from light green to dark brown. (OPTION A)

(3) When sulphur dioxide reacts with water it forms sulphurous acid. (OPTION B)

Explanation

DECOMPOSITION REACTION -

• The reaction in which reactant decomposes to form two or more products.
• The reaction can be exothermic and endothermic.
• In the reaction, ferrous sulphate crystals consist of water of crystallization and are green in color.
• The crystals on heating, lose water to form anhydrous ferrous sulphate that are white in color.
• On heating further, the anhydrous crystals decompose to form a dark brown color solution of ferric oxide.
• Along with this, sulphur dioxide and sulphur trioxide gases are evolved with a pungent smell.
• The reaction involved is -

                          $FeSO_4. H_2O$ → $Fe_2O_3 + SO_2 + SO_3$

• When ferric oxide is reacted with water, it forms sulphurous acid.
• The reaction is - $Fe_2O_3 + H_2O$ → $Fe + H_2SO_3$
• Sulphurous acid is a dibasic or weak acid that has a pungent smell.