Sulphide ions react with Na2[Fe(NO)(CN)5] to form a purple coloured compound Na4[Fe(CN)5(NOS)]. In t — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: In sodium nitroprusside, Na2[Fe(CN)5(NO)], iron is in the +2 oxidation state (coordinated to a nitrosyl cation, NO+). Step 2: Sulfide ions (S2-) attack the coordinated nitrosyl ligand to form the thionitrosyl complex anion, [Fe(CN)5(NOS)]4-. Step 3: The oxidation state of the central iron atom remains +2 throughout this reaction, meaning it does not change, matching option (d).