An inorganic red coloured compound (A) on heating gives a compound (B) and a gas (C). (A) on treatme — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Identify the gas based on the chemical tests described. Both CO2 and SO2 gases turn lime water milky due to the formation of insoluble CaCO3 or CaSO3. Step 2: However, only SO2 is a reducing agent that can reduce orange acidified potassium dichromate (Cr2O7^2-) to green chromium(III) (Cr3+). CO2 is fully oxidized and cannot react with dichromate. Step 3: Since sulfur dioxide (SO2) gas is evolved, the original salt must contain sulfite (SO32-) ions, matching option (d).