A pale yellow precipitate and a gas with pungent odour are formed on warming dilute hydrochloric aci — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Reacting thiosulfate (S2O32-) with dilute mineral acids like HCl leads to protonation and decomposition. Step 2: The reaction yields colloidal sulfur (appearing as a pale yellow precipitate) and sulfur dioxide gas (possessing a pungent, suffocating odor): S2O32- + 2H+ -> S↓ + SO2↑ + H2O. Step 3: This characteristic behavior uniquely identifies the thiosulfate ion, matching option (c).