Quick Q - Sulphate reducing bacteria (1 Viewer)

[meLoncoLLie]

Okay so the bacteria reduces sulphate and eventually the iron becomes corroded. The products should be FeS and Fe(OH)₂ right? I'm assuming that due to the lack of oxygen at great depths, the Fe(OH)₂ will NOT oxidise to form Fe₂O₃.H₂O (rust), is that correct?

Conquering Chem supports this, but in Macquarie, at the bottom of pg 158 there are a few equations that contradict this. Sure, there is SOME oxygen down there, but should we worry about Fe₂O₃.H₂O forming at all?

 

[Abtari]

ok, for that sulphate reducing bacteria dotpoint, i think u only need to know:

how iron is oxidised
what is reduced along with the oxidation of iron

the products formed arent that relevant or necessary, in any case. don't worry about it too much.

 

[serge]

the hole point of SRB is that oxygen is not being reduced
but sulfate is

i wouldnt add the basic corrosion equations if they ask for SRB
just stick to the FeS

 

[Casmira]

Same, if you're unsure about further oxidation to the iron just talk about how iron is oxidised as its a electron source for sulfate reducing bactiera

here are my notes, good luck gloria i wish you the best:
Students learn to:
• Explain that shipwrecks at great depths are corroded by electrochemical reactions and by anaerobic bacteria
• Describe the action of the sulfate reducing bacteria around deep wrecks

Sulfate reducing bacteria (sporovibrio desulfuricans) and other bacteria is responsible for the corrosion of deep wrecks in low oxygen environments. This process occurs as the sulfate-reducing bacteria obtains its energy by reducing sulfate ions from seawater to hydrogen sulfide, this occurs best in acidic water.

SO42-(aq) + 10H+(aq) + 8e- * H2S(aq) + 4H2O(l)

The electrons for the sulfate reduction process can come from oxidation of metals such as Iron.

Fe(s) + Fe2+(aq) + 2e-

The Hydrogen Sulfide forms insoluble sulfides with metal ions, H+ ions are released in this process.

Fe2+(aq) + H2S(aq) * FeS(s) + 2H+(aq)

The metal ions can also react with water to form Iron(II) Hydroxide and produce hydrogen ions.

Fe2+(aq) + 2H2O(l) * Fe(OH)2(s) + 2H+(aq)

 

[Abtari]

ok i think i have an answer for ur question.

NO. you dont write that oxidation bit because the whole point of this focus is we're discussing anaerobic conditions, hence there wouldnt be the oxidation of fe(OH)2 to Fe2O3 or whatever.

 

[serge]

casmira's last equation is still worth knowing
(it's still valid for SRB)

 

[Abtari]

casmira's last equation is still worth knowing
(it's still valid for SRB)

what do u mean by 'still'?

when did we doubt its importance in this topic of sulfate-reducing bacteria

i thought the centre of discussoin was about whether to put/not put the oxidation of Fe(OH)2 to Fe2O3.H2O as pointed out in the first post in this thread

 

[serge]

i thought you dismissed it?
I guess not

 

[meLoncoLLie]

It seems like MANY products form from deep sea corrosion. They include FeS, Fe(OH)₂, Fe(OH)₃, etc etc I can't remember them all. And yeah there is some Fe₂O₃.H₂O as well. But we only need to know the first two.

Thanks guys. And thanks Stephen, good luck to you too! By the way those notes resemble Jenny's

 

[Forbidden.]

From Excel HSC Chemistry, C.M.Roebuck, page 157:


SO₄^2-(aq) -- (anaerobic bacteria in mud) --> S^2-(aq)

Fe(s) + acidic environment --> Fe²⁺

Fe²⁺(aq) + S^2-(aq) --> FeS(s)

FeS(s) is iron(III) sulfide.

I'm going to learn these only.