An amorphous solid "A" burns in air to form a gas "B" which turns lime water milky. The gas is also produced as a by-product during roasting of sulphide ore. This gas decolourises acidified aqueous KMnO_4 solution and reduces Fe^(3+) to Fe^(2+). Identify the solid "A" and the gas "B" and write the reactions involved.

An amorphous solid "A" burns in air to form a gas "B" which turns lime

1.	An amorphous solid "A" burns in air to form a gas "B" which turns lime water milky. The gas is also produced as a by-product during roasting of sulphide ore. This gas decolourises acidified aqueous KMnO_4 solution and reduces Fe^(3+) to Fe^(2+). Identify the solid "A" and the gas "B" and write the reactions involved.
Answer» Solution :The solid A is sulphur , `S_8` and the gas B is `SO_2`. The reactions are given as under : `S_8 + 8O_2 OVERSET(Delta)to 8SO_2` `2MnO_4^(-) + 5SO_2 + 2H_2O to 5SO_4^(2-) + 4H^(+) + underset("(Colourless)")(2MN^(2+))` `2Fe^(3+) + SO_2 + 2H_2O to 2Fe^(2+) + SO_4^(2-) + 4H^(+)` `SO_2` is produced as a by - product during roasting of sulphide ore. The sulphides are converted into oxideswith the EVOLUTION of `SO_2`.