A Question A day (1 Viewer)

[Budz]

although i wont be online everyday, someone i sure would post a question in this thread..
according to my chem teacher...
A question a day keeps failing away.

heres just a simple question to get started...

Name the electrolytes adn electrodes required in the extraction of pure sodium?

 

[xiao1985]

electroylte: molten NaCl
electrode Pt

 

[Budz]

yes... too easy
um another question
for the chemistry and conservation ppl
Identify the role of sulphate reducing bacteria in deep shipwrecks?

 

[imano]

hey all im new and i was wondering if any of u had any notes for prelim chemistry

 

[azza_3761]

hey all im new and i was wondering if any of u had any notes for prelim chemistry

Take a look at http://www.boredofstudies.org/view.php?course=11

 

[Budz]

hey what happened to the question

 

[thunderdax]

I've got a question for you budz: Do you really expect anyone from school in 2005 to have finished shipwrecks yet?

 

[xiao1985]

I've got a question for you budz: Do you really expect anyone from school in 2005 to have finished shipwrecks yet?

some school might have started shipwrecks before monitoring...
and he's just trying to help.... don't be too harsh on him...

and besides... even if school didn't go over shipwrecks, students can always find answers in their text books... frankly that's how study in general should be done... u are encountered a problem and u dig for answers... not jsut waiting at school to be spoon fed answers from ur teachers...

 

[ishq]

yes... too easy
um another question
for the chemistry and conservation ppl
Identify the role of sulphate reducing bacteria in deep shipwrecks?

The anaerobic sulfur reducing bacteria eg. Thiobacillus, change the reaction which occurs at the cathode and cause the Iron to oxidise at the anode. In their presence -

Cathode:
SO4(2-) +8e(-) +5H2O ----> 9OH(-) + HS (-)
Anode:
4Fe ----> 4Fe(2+) + 8e(-)

Fe(2+) reacts with OH(-) and HS(-) to form Fes and Fe(OH)2. Black Fe(II) Sulfide forms on the steel along with Iron(II) hydroxide, which, in the absence of aur, is not converted into Iron(III) as in normal corrosion.

Also, due to the high microbiological activity, the pH of the water decreases. Acidic environments accelerate the rate of corrosion.

[/splurting of information]

We just finished the top last term - its too fresh in my memory.

Question for Shipwrecks/Conservation - Describe, using examples, the process of Cathodic Protection.

 

[Dreamerish*~]

ok um...
most schools are probably doing module 1, then 2, then 3, then options, and right now my school is up to monitoring.

thunderdax was a bit harsh, but he was right. if HSC students want to answer questions in this thread, could you please post questions that are from module 2 or earlier? it would be good to revise past topics and test what we recently have learnt.

otherwise it will be just 2004 students answering all the questions

 

[ishq]

I take it I'm an anomaly then?

 

[tennille]

This is for your question on cathodic protection.

Basically, you can attach a corrosive metal to iron, for example, which results in the more corrosive metal corroding preferentially instead of the iron. When you attach the block of zinc, for example, to iron, an electrochemical cell is generated where zinc acts as the anode. The elctrons flow into the iron, which stop it from forming Fe ions and therefore corroding--> zinc is know as the sacraficial anode.

This can be used in ships, where a few blocks of zinc are attached to the ship.

Another form of cathodic protection is the impressed current method. DC current flows through an inert metal or graphite, which provides electrons to the "other" metal to stop it from corroding. This is used in pipes and in order for this to work, the surroundings must be moist so that the circuit can be complete by the movement of electrolytes through each electrode.

hsc.csu.edu.au as a lot of information on shipwrecks.

 

[Dreamerish*~]

I take it I'm an anomaly then?

how is your school doing it?
but most schools are going in the M123-option order...
i'd read ahead, but i've discovered that i do a lot better in my exams if i just stick to what i'm doing at the moment and revise it thoroughly.

 

[xiao1985]

@tennille, stop ruining the fun of 05ers =p, ok jsut realise that's very hypocritical of me but any way~~~

here's a q from acid and base... not very syllabus related, but prac related:
during titration of CH3COOH, with NaOH, john added 10ml of phenolphthalein ... his justification being that "if you add more indicator, colour change is easier to see... hence u can more accurately determine the end pt much precisely."
Sarah on the other hand said "but too much of anything is not good."
who's right?! justify...

only the 05'ers plz... pre 05'ers can just go n busy with their asgmts (whcih i am sure they ahve many)

 

[ishq]

how is your school doing it?
but most schools are going in the M123-option order...
i'd read ahead, but i've discovered that i do a lot better in my exams if i just stick to what i'm doing at the moment and revise it thoroughly.

Our order in school -
3/4 of PoM
3/4 of Shipwrecks
Last 1/4 of PoM
Last 1/4 of Shipwrecks
TAE
MoM

 

[Budz]

And considering that the end of Prod of materials is REDOX and the entire Shipwrecks course is Redox would it not be logical to go from POM to shipwrecks???

 

[Budz]

Another question

Define an electrolytic cell and how the concentration of electrolytes affect electrolytic reactions.

 

[azza_3761]

@tennille, stop ruining the fun of 05ers =p, ok jsut realise that's very hypocritical of me but any way~~~

here's a q from acid and base... not very syllabus related, but prac related:
during titration of CH3COOH, with NaOH, john added 10ml of phenolphthalein ... his justification being that "if you add more indicator, colour change is easier to see... hence u can more accurately determine the end pt much precisely."
Sarah on the other hand said "but too much of anything is not good."
who's right?! justify...

only the 05'ers plz... pre 05'ers can just go n busy with their asgmts (whcih i am sure they ahve many)

John would be just wasting a hell of a lot of indicator but it would depend upon the amount of solution that you have. With anything under 1L i wouldn't see why you would need more than 10 drops let alone 10 mL. But it wouldn't affect the overall results either way as phenolphtalein is colourless untill its in strongly basic solutions.

 

[NightShadow]

actually the phenolphthalein is actually slightly acidic or something so in a titration you shouldn't use a WHOLE LOT because the phenolphthalein would have to react to change colour detracting from the actual intended reaction of the Naoh and the ch3cooh, besides...its carcinogenic apprantley...for a titration..2-3..drops should be sufficient

 

[xiao1985]

@nightly shadow:
yes, phenolphthalein is acidic by nature ... in fact all acid/base indicator are acidic by nature, hence it is not wise to put too much of them in as they stuff up ur end result...

and u are also right how phenolphthalein maybe carinogenic... quite surprizing in fact, didn'tcome up t o me before =)
nicely done ^^