H2C2O4 gas (A) + gas (B) + liquid (C).<br>Gas (A) burns with a blue flame and is oxidised to gas (B) — p Block Elements Chemistry Question

💡 Solution & Explanation

Step 1: Heating oxalic acid (H2C2O4) yields carbon monoxide (CO, gas A), carbon dioxide (CO2, gas B), and water (H2O, liquid C). CO burns with a blue flame and is oxidized to CO2. Step 2: Carbon monoxide (gas A) reacts with chlorine gas in the presence of sunlight to form phosgene (COCl2, compound D). Phosgene reacts with ammonia (NH3) under heating to form urea (NH2CONH2, compound E). Step 3: Therefore, the substances A, B, C, and E are CO, CO2, H2O, and NH2CONH2 respectively, which corresponds to option (c).