An amorphous solid (A) burns in air to form a gas (B) which turns lime water milky . The gas is also produced as a byproductduring roasting of sulphide ore. This gas decolourises acidifiedaqueousKMnO_(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 byproductduring roasting of sulphide ore. This gas decolourises acidifiedaqueousKMnO_(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 the byproduct of roasting to sulphide ore is `SO_(2)`. It turns lime water milky. Therefore, gas 'B'must be `SO_(2)`. (ii) As the gas 'B' is obtained when amorphous solid 'A' burns in air therefore, amorphous solid 'A' must be sulphur `s_(8)`. `underset("(A)")(S_(8))+8O_(2) overset(Delta)RARR underset("(B)")(8SO_(2))` Gas (B) reduces acidified aqueous KMnO4 solution and reduces `Fe^(3+)` to `Fe^(2+)` salts as shown below: `underset("(yellow)")(2MnO_(4)^(-))+underset("(B)")(SO_(2))+2H_(2)O rarr underset("(GREEN)")(2Fe^(2+)+SO_(4)^(2-)+4H^(+))` (IV) Thus, solid 'A' is `S_(8)` and gas 'B' is `SO_(2)`.