A water-soluble salt X reacts with dilute H ₂ SO ₄ to release a gas Y that smells of rotten eggs. When an aqueous solution of X is treated with sodium nitroprusside solution, a purple-coloured complex Z is formed. Identify the gas Y and the formula of the complex Z .

Step-by-step solution

The gas Y evolved with dilute H ₂ SO ₄ having a rotten egg smell is hydrogen sulphide ( H ₂ S ). This indicates the presence of sulphide ( S ²⁻ ) ions in the salt X . As a confirmatory test, when an aqueous solution of a sulphide salt is treated with sodium nitroprusside ( Na ₂[ Fe ( CN )₅ NO ] ), a purple-coloured complex is formed due to the formation of sodium thionitroprusside. S ²⁻ + [ Fe ( CN )₅ NO ]²⁻ [ Fe ( CN )₅ NOS ]⁴⁻ Thus, the purple complex Z is Na ₄[ Fe ( CN )₅ NOS ] . Answer: Y = H ₂ S , Z = Na ₄[ Fe