Question

5.During the experiment of heating of ferrous sulphate crystals,
four students recorded their observations as:
i) Green colour of crystals changes to brown black colour
ii) Brownish yellow gas is evolved
iii) Blue colour of crystals changes to green colour
iv) Smell of burning sulphur is felt
The correct set of observations are
a) i and iii
b) i and iv
c) ii and iii
d) iïi and iv​

Answer 1

Answer:

answer is option B.

Explanation:

ferrous sulphate crystals are green in colour and on heating they turn brown because of formations of ferrous oxide.

also due to release of SO2 (sulphur dioxide) and SO3(sulphur trioxide) it gives the smell of burning sulphur.

FeSO4--(on heating)-----> Fe2O3+SO2+SO3

Answer 2

During the experiment of heating of ferrous sulphate crystals, four students recorded their observations as:  Green colour of crystals changes to brown black colour and Smell of burning sulphur is felt.

• Ferrous sulfate crystals are green in color.

• Ferrous sulfate crystals contain water molecules (FeSO4. 7H2O) when heated.  On heating, ferrous sulfate crystals lose water and anhydrous ferrous sulfate (FeSO4) is formed.  Hence their color changes from light green to white.

color of ferrous sulfate crystals

• Ferrous sulfate crystals contain water of crystallization (FeSO4.7H2O).

• Ferrous sulfate crystals are light green in colour.

  color after heating

• The color changes from pale green to white due to the formation of anhydrous ferrous sulphate FeSO4.

• On further heating, anhydrous ferrous sulfate decomposes to form ferric oxide (Fe2O3), sulfur dioxide (SO2) and sulfur trioxide (SO3).  Hence, the emitted gas smells like burning sulphur.

 In this reaction, the single reactant FeSO4 decomposes to produce three different products.  This reaction is a decomposition reaction.

                    2FeSO4(s)→Fe2O3(s)+SO2(g)+SO3(g)

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