Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12
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How is the presence of SO2 detected? - Chemistry

How is the presence of SO2 detected?

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Solution 1

SO2 is a colourless and pungent smelling gas.

It can be detected with the help of potassium permanganate solution. When SO2 is passed through an acidified potassium permanganate solution, it decolonizes the solution as it reduces `MnO_4^(-)` ions to `Mn^(2+)`  ions

`5SO_2 + 2MnO_4^(-) + 2H_2O -> 5SO_4^(2-) + 4H^(+) + 2Mn^(2+)`

Solution 2

SOis a pungent smelling gas. It can be detected by two test:

SO2 turn pink color of KMnO4 to colourless due to reduction of `MnO_4^(-)` to `Mn^(2+)`

`2MnO_4^(-) + 5SO_2+ 2H_2O -> 2Mn^(2+)  + 5SO_4^(2-) + 4H^(+)`

(Pink)                                                (colourless)

 

2) It turn orange colour of acidified `K_2Cr_2O_7` to green due to reduction of `Cr_2O_7^(2-)` to `Cr^(3+)`

`Cr_2O_7^(2-) + 3SO_2 + 2H^(+) -> 2Cr^(3+) + 3SO_4^(2-) + H_2O`

(orange)                                        (green)

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APPEARS IN

NCERT Class 12 Chemistry Textbook
Chapter 7 The p-block Elements
Q 22 | Page 189
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