Iron fillings 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?

When iron fillings and sulphur is heated it will give the following reaction:
$Fe(s)+S(s) → FeS$

When HCl is added to this mixture Ferric chloride is produced and Hydrogen sulphide gas is produced. A foul rotten egg smell of Hydrogen sulphide is the indicator of H2S production.
$FeS + 2HCl \rightarrow FeCl_2 + H_2S$

When dilute HCl is added to this setup B, Hydrogen gas is evolved and sulphur does not take part in the reaction. When a burning matchstick is brought near the evolved gas, the matchstick burns with a pop. This is the indication of the production of Hydrogen gas.
$Fe + 2HCl \rightarrow FeCl_2 + H_2$

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