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 :(i) Since gas 'B' is obtained as a by -product during roasting of sulphide, THEREFORE, gas 'B' must be `SO_(2)`. `2ZnS+3O_(2)to2ZnO+2SO_(2)(B)` (ii) Since gas 'B' is obtained when amorphous solid 'A' burns in air, therefore, amorphous solid 'A' must be sulphur, `S_(8)`. `S_(8)(A)+8O_()to8S_(2)(B)` (iii) Gas 'B' reduces acidified `KMnO_(4)` solution and reduces `FE^(3+)" to "Fe^(2+)` salts as shown below : `{:underset("Purple")(2MnO_(4)^(-))+underset((B))5SO_(2)+2H_(2)Otounderset("COLOURLESS")(2Mn^(2+))+5SO_(4)^(2-)+4H^(+):}` `{:underset(("Yellow"))(2Fe^(3+))+underset((B))SO_(2)+2H_(2)Otounderset(("Green"))(2Fe^(2+))+SO_(4)^(2-)+4H^(+):}` Thus, solid 'A' = `S_(8)` and gas 'B' = `SO_(2)`.