In the laboratory, a gas is produced by adding a dilute acid to a metal sulfide. The gas has the odor of rotten eggs and turns lead(II) acetate paper black. Which gas is it?
Show the answer and explanation
Correct answer
A. Hydrogen sulfide
Principle or equation
Hydrogen sulfide (H2S) is produced by the reaction of a metal sulfide with a dilute acid. It has a characteristic rotten egg odor and reacts with lead(II) acetate to form black lead(II) sulfide.
Why this answer is correct
When dilute hydrochloric acid is added to iron(II) sulfide, hydrogen sulfide gas is evolved: FeS + 2HCl → FeCl2 + H2S. H2S turns lead(II) acetate paper black due to formation of PbS.
Example
FeS + H2SO4 → FeSO4 + H2S.
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