A Complication with the Production of Gases

H₂S is a gas under normal circumstances. In fact, this gas is the compound responsible for the smell of rotten eggs.

The other three of the gases mentioned before are not actually gases. They are unstable compounds that immediately decompose to form gases.

\(H_2CO_3 \rightarrow H_2O + CO_2\) 

\(H_2SO_3 \rightarrow H_2O + SO_2\)

\(NH_4OH \rightarrow H_2O + NH_3\) 

That means that the reaction between HCl and Li₂CO₃ could be written 2 ways:
\(2HCl + Li_2CO_3 \rightarrow H_2CO_3 + 2 LiCl\)

or

\(2HCl + Li_2CO_3 \rightarrow H_2O + CO_2 + 2 LiCl\)

The second is more complicated, but also more honest.