shipwrecks, corrosion n conservation (3 Viewers)

[Captain Gh3y]

hey guys ive been talkin to some teachers that were bitching to me, like in physics, music etc and this is the general gist ive gotten from them, explaining the 7 mark question:

(call me sexist but this is pretty factual)

Studies have proven that girls answer essay questions better than scientific short answers and that stuff, whilst guys are better at short answers and not so good at the essay stuff. It may not be so for you, but in general its true.
The board of studies about 7 years ago noticed that there werent enough girls doing some subjects, most obviously the sciences, chemistry, physics etc so to encourage more girls to do the course they've made it more of an essay based course, however in doing so (most obvious in physics) they've lost the gist of the subject, and then arent really teaching 'real' (university) physics, hence why ppl r often shocked when they decide to do a science at uni, its much more in depth and factual than the course.
So the essays are to attract girls to the course, hence the essay-ish 7 marker, obviously chemistry is taking the same turn as physics.

You may be right, but that's not the reason.

In physics, it's because it's politically incorrect to expect physics students to also be maths students. That is, they decided to make the physics course accessible to even those who failed year 10 maths (it only requires ~year 8 level algebra/equations). Having said that, don't diss the physics course.

Chemistry never had that much maths to begin with though, so I think in this case it's more to make the course 'trendy' and 'modern' (like the English course). Look at the amount of "impact on envirnoment/society" dotpoints. It's not necessarily to appeal to girls; girls don't write the syllabus. Trendy, 'modern' academics write the syllabus.

...

On topic: I wrote that a galvanic cell was created (Mg anode, Fe cathode) and then described the equations, observations of metals coming in/out of solution and changes in concentration of the solutions, and that therefore the Iron would not rust because it was being protected by the mg.

 

[falltopieces]

did everyone put oxygen as a factor influencing the rate of corrosion?...or anaerobic bacteria?

oxygen , temperature and anaerobic bacteria

 

[AreYouAlright?]

yeah i said the nail also rusted because it wasnt connected to the magnesium and therefore wasnt cathodically protected...also when iron ions are displaced by the magnesium, the magnesium ribbon would dissapear into solution or untill all the iron ions had been removed .

but also the iron forming on the magnesium may eventually rust also..?

No! Unless i'm mistake the Iron nail would not rust... as if you put and iron nail in a solution of Iron does it rust.....? If you put an iron nail in a solution of magnesium it does not displace it either as magnesium is a stronger reductant.

Am i right?


Also... there is no deposit on the iron nail as it does not form a galvanic cell, there is no external wire connecting the two metals so how would electrons flow between?

 

[holla back girl]

its a GALVANIC CELL

we're just not used to seeing two metals in the same beaker

 

[MuffinMan]

haha true that

 

[serge]

ummm they said deep sea wrecks....that means the concentation of oxygen....but it said rate of corrosion...then agian it could be bacteria.... prob either answer is fine

I dont think so, there's a separate dotpoint for deep-sea corrosion

its a GALVANIC CELL

we're just not used to seeing two metals in the same beaker

no, they're two un-connected half cells?

who mentioned that the iron nail would rust?

No! Unless i'm mistake the Iron nail would not rust... as if you put and iron nail in a solution of Iron does it rust.....?

you are mistaken, solution means water as well, and most water has some dissolved oxygen in it

 

[gogogadgetbrain]

its a GALVANIC CELL

we're just not used to seeing two metals in the same beaker

i dont think so.. galvanic cell implies that the electron transfer process occurs through an external conductor

i believe its simply a redox reaction at the magnesium where
Mg(s) + Fe2+(aq) -> Mg2+(aq) + Fe(s)

and the iron will rust as there is still water and oxygen present- i dont think the iron will be protected at there is no direct path for the electrons from the magnesium to the iron...

 

[AreYouAlright?]

its a GALVANIC CELL

we're just not used to seeing two metals in the same beaker

I'm sure you will recall from the work of Alessandro volta and Galvani that two different metal wires joined together in an electrolyte will create a galvanic cell... there is the ability for the ions to move between the two but please, kindly explain to me how an electron would get from one to the other.

I am sure of it, they are simply metal displacement reactions

I agree... there may be scope for rusting but it certainly wouldn't have a metal displacement reaction as the Magnesium solution nor the Iron solution is less active than iron itself.... in fact the idea that the magnesium solution is more active than the Iron might suggest it would stop corrosion... i'm not sure exactly about the extent of rust over only 3 days or so.

 

[MuffinMan]

lol that question...umm i forgot what i put actually...but i hope its right

 

[Abtari]

the beaker that the student set up is NOT a galvanic cell, as such, because the reactions that take place aren't physically separated and there isn't an external conductor that carries electrons from one electrode to the next and so forth....

butttttt

it follows the same principles of a galvanic cell - it involves metallic displacement. i.e. more active metal (i.e. the metal with lower reduction potential) gets oxidised and goes into solution, whereas the ions of the less active metal (i.e. the metal with higher reduction potential) gets reduced and deposits on the metal related to it... remember that there were solutions of both magnesium sulfate and iron sulphate.

Hence, you would get the gradual decrease in the mass of Magnesium strip and the gradual deposition of iron on the iron nail. Furthermore, you would get an increase in the concentration of Magnesium ions in the beaker, and a decrease in the concentration of Iron ions.

 

[Kd14]

yeah i said the nail also rusted because it wasnt connected to the magnesium and therefore wasnt cathodically protected...also when iron ions are displaced by the magnesium, the magnesium ribbon would dissapear into solution or untill all the iron ions had been removed .

but also the iron forming on the magnesium may eventually rust also..?

YAY! That's what I wrote. Iron rusted cos Mg wasn't connected. I hope its right..

 

[AreYouAlright?]

the beaker that the student set up is NOT a galvanic cell, as such, because the reactions that take place aren't physically separated and there isn't an external conductor that carries electrons from one electrode to the next and so forth....

butttttt

it follows the same principles of a galvanic cell - it involves metallic displacement. i.e. more active metal (i.e. the metal with lower reduction potential) gets oxidised and goes into solution, whereas the ions of the less active metal (i.e. the metal with higher reduction potential) gets reduced and deposits on the metal related to it... remember that there were solutions of both magnesium sulfate and iron sulphate.

Hence, you would get the gradual decrease in the mass of Magnesium strip and the gradual deposition of iron on the iron nail. Furthermore, you would get an increase in the concentration of Magnesium ions in the beaker, and a decrease in the concentration of Iron ions.

I agree with you but i don't believe the solid Iron would form on the nail i would say like a standard metal displacement reaction the iron ions would percipitate solid iron out of the solution which would gather in the bottom of the beaker.

 

[MuffinMan]

lol the exams over...just relax buddies

 

[Abtari]

yeah the two posts above this, are both right...

mixed feelings... *sigh*

 

[Captain Gh3y]

Abtari: I said everything you mentioned but also included the words 'galvanic cell', do you think I'll lose marks for including incorrect information?

 

[jayson]

the beaker that the student set up is NOT a galvanic cell, as such, because the reactions that take place aren't physically separated and there isn't an external conductor that carries electrons from one electrode to the next and so forth....

butttttt

it follows the same principles of a galvanic cell - it involves metallic displacement. i.e. more active metal (i.e. the metal with lower reduction potential) gets oxidised and goes into solution, whereas the ions of the less active metal (i.e. the metal with higher reduction potential) gets reduced and deposits on the metal related to it... remember that there were solutions of both magnesium sulfate and iron sulphate.

Hence, you would get the gradual decrease in the mass of Magnesium strip and the gradual deposition of iron on the iron nail. Furthermore, you would get an increase in the concentration of Magnesium ions in the beaker, and a decrease in the concentration of Iron ions.

exactly wat i wrote....but yeh at least chem is ova....bleh

 

[jonemo]

I agree with you but i don't believe the solid Iron would form on the nail i would say like a standard metal displacement reaction the iron ions would percipitate solid iron out of the solution which would gather in the bottom of the beaker.

Fool!- can u not comprehend the wat Abtari is saying?!
Because Magnesium is more reactive than iron, iron from solution will begin to deposit on the Magnesium strip!
How the heck can iron ions 'precipitate' solid iron?!- rethink wat u say, b4 u say it- it is very disturbing to hear chemistry gone wrong!

 

[jonemo]

Abtari: I said everything you mentioned but also included the words 'galvanic cell', do you think I'll lose marks for including incorrect information?

U fool!- u definitely will lose marks for that foolishly foolish statement, u fool.

 

[AreYouAlright?]

Fool!- can u not comprehend the wat Abtari is saying?!
Because Magnesium is more reactive than iron, iron from solution will begin to deposit on the Magnesium strip!
How the heck can iron ions 'precipitate' solid iron?!- rethink wat u say, b4 u say it- it is very disturbing to hear chemistry gone wrong!

You are a fool, and if i were you i'd be hoping to get 50 in that exam... what Abtari said was that the Iron built up on the iron nail... this is incorrect the iron(II) ions in solution precipitate solid Iron with the electrons from oxidising magnesium and solid iron gaters on the bottom of the beaker.

If you can't comprehend this simple chemical process known as metal displacement reactions... i'm afraid one would hope you did not put down for Chemistry at university.

 

[jonemo]

You are a fool, and if i were you i'd be hoping to get 50 in that exam... what Abtari said was that the Iron built up on the iron nail... this is incorrect the iron(II) ions in solution precipitate solid Iron with the electrons from oxidising magnesium and solid iron gaters on the bottom of the beaker.

If you can't comprehend this simple chemical process known as metal displacement reactions... i'm afraid one would hope you did not put down for Chemistry at university.

Guess wat... ur comment makes no sense watsoever. Tis tru that iron does not build up on the iron nail, however, the iron ions cannot 'precipitate' solid iron either.
Iron only forms on the magnesium strip. And the concentration of magnesium ions increase in the solution, and the conc of iron ions decrease.