An unknown salt treated with dilute evolves a gas with the smell of rotten eggs. This gas turns lead — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

The rotten egg smell is characteristic of Hydrogen Sulphide ($H_2S$) gas, which is evolved from Sulphides ($S^{2-}$) upon treatment with dilute acids. It turns lead acetate paper black due to the formation of $PbS$.