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[McLake]

Originally posted by superhubert
the water around the ships becomes slightly acid and aids corrosion. (i think.)

This is true

 

[BlackJack]

Originally posted by McLake
Leave this thread for a few hours and this happens ...

We'd have to take over at least :]. Otherwise nobody will anwr the questions.

 

[McLake]

Originally posted by BlackJack
We'd have to take over at least :]. Otherwise nobody will anwr the questions.

True ...

 

[BlackJack]

I'll actually post a question.
How likely is it that they'll repeat the 7/8 marker questions form last year as another substantial 4+ marker this year?

And, a quiz. "explain the use of acidic oxides such as sulphur dioxide as food additives."

And, would Na2CO3 be considered as a natural base, and if so, describe where it is found, its pH, chemistry... (y'know, THAT dot point).

 

[McLake]

Originally posted by BlackJack

I'll actually post a question.
How likely is it that they'll repeat the 7/8 marker questions form last year as another substantial 4+ marker this year?

Possible, but unlikely ...

And, a quiz. "explain the use of acidic oxides such as sulphur dioxide as food additives."

SO2 is used as a preservitive to prevent microbe growth ...

And, would Na2CO3 be considered as a natural base, and if so, describe where it is found, its pH, chemistry... (y'know, THAT dot point).

I'd say yes but I don't know the answer to the rest ...

 

[aby]

Originally posted by superhubert
anerobic bacteria don't need oxygen. they survive off sulphate. they reduce the sulphate ions and they react with water molecules to form sulphuric acid H2SO4. and oxygen gas. because they accumulate around ships. the water around the ships becomes slightly acid and aids corrosion. (i think.)

but if the water is originally alkaline, and one change in pH means a ten-fold increase in [H+] as it increases exponentially, then it doesn't seem all that realistic that alkaline conditions could change into acidic by the action of cute & tiny little bacteria..... or am i being too practical ? hehe ok thanks!

 

[BlackJack]

Okay, another quiz: "define corrosion"

edit: actually... aren't there othere effects of SO2 additives...?

 

[Dumbarse]

this is easy but i forget how to do it

find the pH of 0.10 mol/L solutions of HCl, HBr and CH3COOH

i get a pH of 1 for all of them, but i know that not right because ethanoic acid is weak, but how do i get the different pH!?!

 

[spice girl]

You need more than HSC chemistry to figure the pH of ethanoic acid. All you need to know is that it's greater than pH 1.0

 

[McLake]

Originally posted by BlackJack

Okay, another quiz: "define corrosion"

The act of becoming oxidised ...

edit: actually... aren't there othere effects of SO2 additives...?

Not that I can find ...

 

[Ronnie]

but if the water is originally alkaline, and one change in pH means a ten-fold increase in [H+] as it increases exponentially, then it doesn't seem all that realistic that alkaline conditions could change into acidic by the action of cute & tiny little bacteria..... or am i being too practical ? hehe ok thanks! [/B][/QUOTE]

These equations are gonna be a bitch....
Much of the shipwrecks in deep water is caused by certain anaerobic bacteria the reduce sulfate to sulfide ie:

SO4(2-) + 5H20 + 8e- --> HS- + 9OH- Reduction 1/2

4Fe --> 4Fe(2+) + 8e- Oxidation 1/2

Hence the redox reaction is given by

4Fe(2+) + SO4(2-) + 5H2O --> 4Fe(2+) + HS- + 9OH-

however the Fe(2+) formed reacts with HS- and OH- to form insoluble FeS and Fe(OH)2 compounds ie:

4Fe(2+) + HS- + 7OH- --> FeS(s) + 3Fe(OH)2(s) + H2O(l)

hence the overall reaction is given by

4Fe(s) + SO4(2-) (aq) + 5H2O(l) --> FeS(s) + 3 Fe(OH)2(s) + H2O(l) + 2OH- (aq)

The waste from these bacteria that reduces sulfate to sulfide makes the ocean more acidic. Due to the abundance or organic material around shipwrecks, they are able to multiply and rapidly thrive and produce an acidic environment which promotes corrosion (HS- --> H+ + S(2-) )

does that make sense or confuse everyone even more?

 

[Ozz^E]

SO2 use in food additives:

- Used as a chemical preservative for certain foods.
- Prevents growth of microorganisms(moles,bacteria)
- Prevents food from turning brown because of oxidation
- Dreif fruits/wine are foods that can be fumiagted with SO2 gas while in the containers. The acidic environment (air is replaced by SO2) does above mentioned roles.

thats all i know bout it.

 

[Ozz^E]

Originally posted by Dumbarse
this is easy but i forget how to do it

find the pH of 0.10 mol/L solutions of HCl, HBr and CH3COOH

i get a pH of 1 for all of them, but i know that not right because ethanoic acid is weak, but how do i get the different pH!?!

You can only work out pH of strong acids (as yet anyway).

 

[McLake]

OK, new Q's are being accepted, just post it here and I will try to get back to you within 24 hrs ...