# How could you distinguish between CO_2 from H_2S?

Nov 1, 2016

Odour would be the best bet.

#### Explanation:

Hydrogen sulfide, which is poisonous in large enough concentrations (mind you, so is $C {O}_{2}$, but here the concentration would be larger) has quite an offensive odour, which is quite distinctive.

Lead acetate paper is available commercially, and is used as a test for hydrogen sulfide, and gives a grey precipitate of lead sulfide. Carbon dioxide would fail this test.

${H}_{2} S \left(a q\right) + P b {\left(O A c\right)}_{2} \left(a q\right) \rightarrow P b S \left(s\right) \downarrow + 2 H O A c$.