An amorphous soild 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 sulohide 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.

Explanation

The available information suggests that the amorphous solid "A" is sulphur. It exists as `S_(8)` molecule and burns in air to form sulphur dioxide `(SO_(2))` gas "B". The gas turns lime water milky due to the formation of a compound calcium sulphite `(CaSO_(3))`
`underset("A")(S_(8))+underset(("Air"))(8O_(2)(g))overset("heat")to underset("B")(8SO_(2)(g))`
`underset("Lime water")(Ca(OH)_(2)(aq))+SO_(2)(g) ot underset(("Milky"))(CaSO_(3)(s))+H_(2)O(aq)` The gas is produced as a by-product during the roasting of sulphide ore such as zinc blende (ZnS)
`2ZnS(s) +3 O_(2)(g) overset("heat") to 2ZnO(s) + 2SO_(2)(g)`
The gas decolourises acidified aqueous `KMnO_(4)` solution and reduces compounds like `Fe_(2)(SO_(4))_(3)` containing `Fe^(3+)` ions to `FeSO_(4)` containing `Fe^(2+)` ions
`2KMnO_(4)underset(("Pink"))(aq)+5SO_(2)(g)+2H_(2)O(aq) to underset("Colourless") K_(2)SO_(4)(aq) +2MnSO_(4) underset("Colourless") (aq)+2H_(2)SO_(4)(aq)`