Gas that cannot be collected over water is : — Redox Reactions and Volumetric Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Potassium tetracyanocadmate(II), K2[Cd(CN)4], is a soluble complex in water. Step 2: Passing H2S gas through this solution decomposes the relatively less stable cadmium complex to precipitate highly insoluble yellow cadmium sulfide, CdS↓. Step 3: Since a solid precipitate forms from a soluble starting material, this is a precipitate formation reaction (type A), corresponding to option (a).