An orange solid (X) on heating gives a colourless gas (Y) and only a green residue (Z). Gas (Y) on t — p Block Elements Chemistry Question

💡 Solution & Explanation

Step 1: The physical properties of Group 16 hydrides (H2O, H2S, H2Se, H2Te) like melting point, boiling point, and critical temperature do not change regularly due to strong intermolecular hydrogen bonding in water (H2O). Step 2: Thermal stability depends on the M-H bond dissociation energy. As the central atom size increases down the group, the M-H bond length increases and bond strength systematically decreases. Step 3: Consequently, thermal stability decreases monotonically and regularly down the group (H2O > H2S > H2Se > H2Te), making option (b) the correct statement.