Q35Long answer
Iron filings and sulphur were mixed together and divided into two parts, ‘A’ and ‘B’. Part ‘A’ was heated strongly while Part ‘B’ was not heated. Dilute hydrochloric acid was added to both the Parts and evolution of gas was seen in both the cases. How will you identify the gases evolved?
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Part A Fe (s) + S (s) Heat FeS (s) FeS + 2 HCl (aq) → FeCl2 + H2 S Part B Fe (s) + S (s)→ Mixture of iron filings and sulphur When dilute HCl is added to it Fe (s) + S (s) + 2 HCl (aq) → FeCl2 + H2 gas Sulphur remains unreacted H2S gas formed has a foul smell and on passing through lead acetate solution, it turns the solution black. Hydrogen gas burns with a pop sound.