The Formation of Bromine in Manufacturing: How Does It Work?

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Discussion Overview

The discussion revolves around the chemical processes involved in the formation of bromine from sodium bromide in seawater, specifically focusing on the steps of passing chlorine into seawater, the subsequent reactions, and the conditions affecting bromine extraction. The scope includes theoretical chemistry and chemical reactions relevant to manufacturing processes.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant provides a reaction equation for the first step involving chlorine and sodium bromide, suggesting Cl2 + NaBr ----> NaCl + Br2.
  • Another participant expresses confusion regarding the interpretation of the mole ratio in the context of sodium bromate(V) formation.
  • Disproportionation of bromine into bromide and bromate is mentioned as a relevant process, with questions about how these products yield bromine upon acidification.
  • A participant introduces the concept of "pH dependent equilibrium" in relation to the extraction process.
  • There is a discussion about the alkaline nature of sodium carbonate and its effect on pH, leading to uncertainty about the acidification process.
  • A balanced reaction equation involving bromine and hydroxide ions is suggested, indicating a pH dependency in the reactions.
  • One participant notes the stoichiometric ratio of 1:5 and questions the reversibility of the reaction, referencing Le Chatelier's principle to explain the effects of changing pH on bromine production.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and confusion regarding the chemical processes, particularly the role of pH and the reversibility of reactions. There is no consensus on the interpretation of the mole ratio or the specifics of the acidification process.

Contextual Notes

Limitations include the lack of clarity on the specific reactions involved in the acidification step and the dependence on pH levels, which may not be fully resolved in the discussion.

Kushal
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Homework Statement



Bromine is obtained from the sodium bromide dissolved in sea water by:

I passing chlorine into sea water at pH 3.5

II blowing out the bromine with air and absorbing it in aqueous sodium carbonate

III acidifying the solution and distilling out the bromine.

(i) Write an equation for step I.

(ii) Step II produces a solution of sodium bromate(V), NaBrO3 in the molar ratio 1:5.

Construct an equation for the formation of the bromine in step III.


The Attempt at a Solution



(i) Cl2 + NaBr ----> NaCl + Br2

(ii) i have no idea how to interpret the information provided in this part. how can the mole ratio help me?

thnks
 
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Google disproportionation.
 
i didn't think of the disproportionation of bromine into bromide Br- and bromate BrO3-.

thnks

but how does either of the products give bromine upon acidification?

is it a similar reaction as acid + carbonate?
 
I would call it "pH dependent equilbrium".
 
i tried googling pH dependent equilibrium but i couldn't find something specific to the bromine extraction reaction.
sodium carbonate is alkaline. the pH would be around 9-10. acidifying the solution would decrease the pH...

i'm lost...
 
You are close. Just write balanced reaction equation Br2 + OH- and you will see that it is pH dependent. LeChetelier's priniciple is enough to explain what is going on.
 
3Br2 + 6OH- ----> 5Br- + BrO3- + 3H2O

ahhh... now i get why the ratio is 1:5...

is the reaction reversible?

if this is the case, as you add H+, the concentration of OH- decrease. according to LCP the backward reaction is favoured, producing more Br2
 

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