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Test for Sulfur Dioxide Gas,  SO_2(g).

Sulfur Dioxide

1)  Has no colour.

2)  Has a choking smell.

3)  Will turn moist blue litmus paper red,
or moist universal indicator paper red - it is acidic.

4)  Will put out a lit splint.

Specific test.

Sulfur dioxide will turn acidified
potassium dichromate(VI) solution from orange to green.
Chromium is reduced from (VI) to (III).

       potassium        sulfur    sulfuric     chromium(III)    potassium          
  dichromate(VI) + dioxide   +  acid         sulfate    +    sulfate   +  water.

K₂Cr₂O_7(aq)  +    3SO_2(g) +  H₂SO_4(aq) Cr₂(SO₄)_3(aq) +  K₂SO_4(aq)  + H₂O_(l)

Collecting Sulfur Dioxide.

Sulfur Dioxide is more dense than air
and can be collected by downward delivery or using a gas syringe.

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