Sciencemadness Discussion Board

Generating acid via hydrogen gas

sternman318 - 1-6-2011 at 13:21

Is it possible to generate acids by bubbling hydrogen gas through an aqueous solution of an oxidizer ( such as KMnO4)? Google doesn't yield much, and neither does my mind xD

hkparker - 1-6-2011 at 13:35

The hydrogen would have to ionize and something in solution would have to reduce. You mean like a simple single displacement?

H<sub>2</sub> + MA --> HA + M?

In that case hydrogen would have to be a stronger reducing agent, so I think this reaction could work with some not very reactive metals, like silver:

H<sub>2</sub> + AgNO<sub>3</sub> --> HNO<sub>3</sub> + Ag

Of course nitric acid attacks silver though so....
maybe a reaction between dry hydrogen gas and dry silver chloride at high temperatures would produce HCl gas and silver.

Such reactions would obviously not work with an alkali metal as your cation.

[Edited on 1-6-2011 by hkparker]

m1tanker78 - 1-6-2011 at 13:47

AFAIK, H2 will not readily react with, say, Cl2. The H+ species will quickly react with free Cl- to form HCl. You might be confusing the dissolution of Cl2 in H2O? Tuning your google searching to aqueous NaCl electrolysis will probably give you a good starting point.

Tank

ScienceSquirrel - 1-6-2011 at 14:29

Not really, you are driving some very favourable chemistry backwards.
Hydrogen is a stable diatomic gas that is not very soluble in water.
For example you would need a metal chloride that is a strong reducing agent for the reaction to work.
Hydrogen would be absorbed, the metal would be reduced and precipitated and hydrogen chloride would pass in to solution.
You would have to get it to work catalytically to make it useful.

sternman318 - 1-6-2011 at 14:49

Quote: Originally posted by ScienceSquirrel  
Not really, you are driving some very favourable chemistry backwards.
Hydrogen is a stable diatomic gas that is not very soluble in water.
For example you would need a metal chloride that is a strong reducing agent for the reaction to work.
Hydrogen would be absorbed, the metal would be reduced and precipitated and hydrogen chloride would pass in to solution.
You would have to get it to work catalytically to make it useful.


Alright, thank you and hparker. One question: why did you both mention the use of a metal that is a strong oxidizing agent ( though you said reducing agent?), why does it require a metal, as opposed to some anionic oxidizing agent? Is it because they all seem to require acidic conditions? I apologize if these are dumb questions, I took chemistry last year and finding out how much I seem to have forgotten

Melgar - 1-6-2011 at 15:52

IIRC, H2 will react with halogens at high temperatures to give the corresponding acids. Might be possible at lower temperatures with perhaps a palladium catalyst. But really, hydrogen is a reducing agent and if you oxidize it you get, wait for it... water. :p

redox - 6-6-2011 at 16:45

It is possible to generate acid by bubbling acetylene through silver nitrate. This is not what you asked for, but it is still the formation of acid with (effectively) neutral compounds:

2AgNO3 + C2H2 = 2HNO3 + Ag2C2

Jor - 6-6-2011 at 17:00

NO! First of all, silver acetylide forms an adduct with HNO3 or AgNO3, I do remember wich.

Second, this stuff is an incredibly sensitive explosive, even 100mg, so this is not practical.

White Yeti - 28-7-2011 at 13:37

You could theoretically make sulfuric acid from copper sulphate and hydrogen gas. But copper and hydrogen are both very close together on the activity series.

AndersHoveland - 28-7-2011 at 13:59

Chlorine spontaneously explodes with hydrogen in sunlight. It is theoretically possibly to just react hydrogen with chlorine together in a glass container, using an continuous electrical igniter to keep the gases constantly burning, otherwise if they are allowed to build up the sudden reaction could blow the lid/hosing off. This would carry a serious danger of explosion of course. Hydrogen chloride is also a gas, but quickly dissolves in water to form hydrochloric acid. Diluting with nitrogen gas might help educe risk of explosion. (probably would not want to use CO2 since traces of phosgene could potentially form)

To summarize, sternman318, if you are asking this type of question, you probably should not be messing around with this type of thing, very dangerous.

Bubbling chlorine gas into a dilute solution of hydrogen peroxide, however, forms hydrochloric acid and gives off oxygen bubbles. (the H2O2 is actually reacting with the hypochlorite ions in equilibrium) The net reaction is:

Cl2 + H2O2 --> (2)HCl + O2

[Edited on 28-7-2011 by AndersHoveland]