question_answer

    Iron filings and sulphur were mixed together and divided into two parts 'A' and 'S'. Part 'A' was heated strongly while Part'S' 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?                         [NCERT Exemplar]

Answer:

        Part A Part B Mixture of iron filings and sulphur When dilute HC1 is added to it 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.