TPRH G CHEM bubbling question

[MrNeuro]

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HBr is gaseous at ambient temperature why isn't bromide ion a plausible answer?


http://i.imgur.com/qNMBu.jpg

 

[MedPR]

Is there more information?

 

[MrNeuro]

Is there more information?

nope

 

[MedPR]

nope

If we don't know what the original sample is, the answer could be anything..

 

[MrNeuro]

If we don't know what the original sample is, the answer could be anything..

solution has ag hg pb cu bi al fe zn ba mg ca sr g1a and NH4

 

[MedPR]

solution has ag hg pb cu bi al fe zn ba mg ca sr g1a and NH4

I would guess Carbonate. HCl + Carbonate salt will form CO2 gas. Even though HBr is gas in ambient conditions, if HCl reacted with some kind of bromide ion base, the bromide would just become aqueous HBr.

And since there's a bunch of cations in solution, it seems reasonable that carbonate could be there.. CaCO3, MgCO3, etc.

So CaCO3, for example:

2HCl(aq) + CaCO3(s) --> CaCl2(aq) + CO2(g) + H2O(l)

 

[chiddler]

HBr is gaseous at ambient temperature why isn't bromide ion a plausible answer?


http://i.imgur.com/qNMBu.jpg

HBr is a strong acid. Even after adding buttloads of HCl, and HBr forms in solution, very little will leave solution.

It's like dissolved oxygen in water. Yeah, it's there. Yeah it can leave solution. But it's in such minute amounts you won't notice. Acid + carbonate is a good answer as medpr said bc CO2 is easily produced in much larger amounts.

 

[typicalindian]

The only thing I can think of is Carbonate ion as well. My reasoning being carbonate is a base so it would react with HCl to produce HCO3 which is also able to react with H+ to form CO2 and H2O. Not sure if that makes sense though...

 

[MrNeuro]

thanks guys makes sense

i swear bicarbonate/carbonic acid kills me everytime i encounter it

 

[kasho11]

Agree with aboves, CO2 is a very common answer for gas evolution questions like this, especially common I have noticed with HCl.

HBr dissolved in solution can really only be removed with a dehydrating agent. Addition of HCl will not cause its evolution. Some common dehydrating reagents are concentrated sulfuric/phosphoric acid and hot aluminum oxide. Slightly beyond the scope of the MCAT but good knowledge nonetheless.

You should be able to reason through and understand that HBr is a strong acid and will therefore dissolve almost entirely in solution and thus the only way to get it out of solution would be to use something that dehydrates it.