Solving gas evolution problems

[ieatshrimp24]

There have been at least a couple of times in recent FLs I've taken that a question asks "which of the following gases evolve from the experiment/reaction?" I've either gotten them right or wrong but they were complete guesses. I know this is really broad, but I'm wondering if anyone knows a way to determine the gas that comes from a reaction. If anyone can provide specific examples, that would be great.

---

Members don't see this ad.

 

[erythrocyte666]

if you see a carbonate (e.g. CaCO3, Na2CO3, etc.), then adding acid will form H2CO3 which separates in H2O and CO2 gas
if you see a sulfite (e.g. CaSO3, etc.), adding acid will form H2SO3 which separates into H2O and SO2 gas
electrolysis of water releases H2 and O2 gases
dehydrogenations can release H2 gases
there are way more examples, but the first one is most prevalent

 

[ieatshrimp24]

if you see a carbonate (e.g. CaCO3, Na2CO3, etc.), then adding acid will form H2CO3 which separates in H2O and CO2 gas
if you see a sulfite (e.g. CaSO3, etc.), adding acid will form H2SO3 which separates into H2O and SO2 gas
electrolysis of water releases H2 and O2 gases
dehydrogenations can release H2 gases
there are way more examples, but the first one is most prevalent

Thanks for this. Hopefully, if a gas evolution problem comes up on the MCAT, it will be one of these examples.