Chemistry HSEB notes | Laboratory preparation of sulfur dioxide gas

Sulfur dioxide gas (SO2) is prepared in the laboratory in following ways :

Theory : Sulfur dioxide gas is prepared in the laboratory by heating copper turnings with conc Sulfuric acid (H₂SO₄) .

Reaction involved :

Cu + conc H₂SO₄ ----------- > CuSO₄ + SO₂ + H₂O

 H₂SO₄ ---------- >SO₂ + H₂O + [  O ]
 Cu + [  O ] ---------- > CuO
 CuO + H₂SO₄ ---------- > CuSO₄ + H₂O

Cu + conc 2 H2SO4 ----------- > CuSO4 + 2 H2O +SO2

Laboratory preparation of sulfur dioxide gas

Procedure :

As shown in the figure, some copper turnings are kept in the round bottom flask which is fitted with thistle funnel and delivery tube.

The other end of delivery tube is kept in a absorption bottle containing conc sulfuric acid. Conc Sulfuric acid is poured in the thistle funnel which reaches to the round bottom flask to start the reaction. Again , one end of delivery tube is kept in absorption bottle and other end is introduced to an erect gas jar for the collection of sulfur dioxide gas by upward displacement of air.

The copper or flask is heated. On doing so the reaction between acid and cupper takes places and sulfur dioxide gas (SO₂) is produce in the flask. The SO₂ gas produced is not  pure so it passed through absorbtion bottle containing con H₂SO₄ to remove moisture from the gas as H₂SO₄ is a great dehydrating agent. After removement of moisture finally, SO₂ gas is collected in the gas jar by upward displacement of air.

Test :

The presence SO₂ gas can be tested by introducing potassium manganese to the mouth of the jar. If it discolourizes then we can know that SO₂ is collected in the jar.

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