Question

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 Parts and evolution of gas was seen in both cases. How will you identify the gases that evolved?

Answer 1

Part A – Iron sulphide is formed which gives out hydrogen sulphide gas with HCI.

\[\ce{FeS + 2HCl -> FeCl2 + H2S}\]

H₂S gas can be identified by its smell. It has a foul smell and it turns lead acetate solution black.
Part B – Fe and S will not react, when HC1 is added to this mixture, only Fe will react with HCI to give out H₂ gas.

\[\ce{Fe + 2HC1 > FeCl2 + H2}\]

Hydrogen gas burns with a pop sound hence can be identified by bringing a burning matchstick near it.