A student prepares a gas by adding dilute hydrochloric acid to solid zinc sulfide. Which test correctly identifies the gas produced?
Show the answer and explanation
Correct answer
D. The gas turns lead(II) ethanoate paper black
Principle or equation
Zinc sulfide reacts with hydrochloric acid to produce hydrogen sulfide gas (H2S). H2S can be identified by its ability to darken lead(II) ethanoate paper due to formation of black lead(II) sulfide.
Why this answer is correct
ZnS(s) + 2HCl(aq) → ZnCl2(aq) + H2S(g). Hydrogen sulfide is a colorless, toxic gas with a rotten egg smell; it reacts with lead(II) ethanoate to form black PbS, so the test is positive. The other tests correspond to O2, H2, and NH3 respectively.
Example
If a gas turns lead(II) ethanoate paper black, it is hydrogen sulfide.
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