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Offline srisiddu

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Hello All
« on: May 25, 2010, 06:04:16 PM »
Can any one suggest a good laboratory method to oxidize HBr to Br2, with possible regeneration of oxidant....
any help is appreciated.

Offline aeacfm

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Re: Hello All
« Reply #1 on: May 30, 2010, 07:13:35 AM »
Because of its commercial availability and long shelf-life, bromine is not typically prepared. Small amounts of bromine can however be generated through the reaction of solid sodium bromide with concentrated sulfuric acid (H2SO4). The first stage is formation of hydrogen bromide (HBr), which is a gas, but under the reaction conditions some of the HBr is oxidized further by the sulfuric acid to form bromine (Br2) and sulfur dioxide (SO2).

NaBr (s) + H2SO4 (aq) → HBr (aq) + NaHSO4 (aq)
2 HBr (aq) + H2SO4 (aq) → Br2 (g) + SO2 (g) + 2 H2O (l)
Similar alternatives, such as the use of dilute hydrochloric acid with sodium hypochlorite, are also available. The most important thing is that the anion of the acid (in the above examples, sulfate and chloride, respectively) be more electronegative than bromine, allowing the substitution reaction to occur.

Offline ajkoer

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Re: Hello All
« Reply #2 on: August 10, 2012, 08:50:02 AM »
Note, I am acquainted with the following reaction involving Chlorine:

Cl2 (g) + H2O + H2SO3 --> HCl + H2SO4

where the volatile HCl can be remove by treating with hot air leaving pure concentrated Sulfuric acid. Actually, this is the oxidation of H2SO3 with HOCl as noted in Watt's Dictionary Chemistry over a century ago:

Cl2 + H2O <--> HCl + HOCl

HOCl + H2SO3 --> HCl + H2SO4.

As such, I would suspect that the reaction you noted is reversible under the proper forcing conditions:

Br2 + H2O + H2SO3 <--> 2 HBr + H2SO4
A good laboratory way to oxidize HBr is to simply add H2O2.

 2 HBr + H2O2 --> Br2 + 2 H2O
« Last Edit: August 10, 2012, 09:06:49 AM by ajkoer »

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