Trick question? Shipwrecks and salvage (1 Viewer)

[bluebiro]

Was the cell diagram doing anything?

My logic being:
-1- It was an electrolytic cell as both Mg? and Fe were in the same solution.
-2- My understanding of electrolytic cells is that you need a battery to drive the reaction and there was no battery.

Seeing that it was worth 4 marks I wrote about anodes and cathodes etc saying something like the iron was oxidised....or some crap like that i cant remember,
anywho what are your thoughts?

 

[muselara]

i dunno but it turned my brain into a milkshake and after lots of thought im pretty sure whatever i ended up writing was right...
it definitely was a question to make you think...much harder than any of the 7 mark questions....it shows that amount of marks definitely doesnt mean difficulty often.

 

[Casmira]

i think of it as this, ions more likely to be a ion so Magnesium sulfate solution conc increases, magnesium strp wears away and iron deposit forms on iron nail and iron sulfate conc decreases

 

[Spadge]

I can't say this with certainty, as it's definately not my strongest suit, but I think a momre reactive metal always displaces a less active metal in solution. Therefore, the aluminium will oxidise, going into the solution, and iron solid should form. Since there are no ions less reactive than iron in solution, the iron doesn't do anything.

 

[Captain Gh3y]

The consensus in the other thread appears to have been that it was just a metal/metal displacement reaction, not a cell.

 

[yumi_cheeseman]

OMG you HAVE to be kidding me right? are you saying you have done the chemistry course, let alone the course in shipwrecks and salvage, which if u think for 2 seconds all of corrosion is BASED on the works of a galvanic cell

yes all electrolytic cells need a power source, but this is a galvanic cell (such as the "first" one created by galvani's frog legs), where the presence of an electrolyte and 2 different metals are needed.

The reason that there was Fe sulfate and Mg sulfate was to make u think which was the reaction was going. To do this u woulda had to go to the back of ur periodic table of elements, and checked which element had a greater oxidising potential. Which of course is Mg, since it is higher.

Therefore what u woulda observed in the experiment would be the corrosion of magnesium, and a build up of iron on the nail.

 

[bluebiro]

cheers...my stupidness
thank god its over :whew:

 

[Haku]

what u guys taliking about?

iron would form on magnesium

but magnesium for an non porous layer so it does corrode. so nothing much would happen

 

[bluebiro]

jeez lumi...sorry if not everyone is as smart as you, or as smart as you think you are. But thanx for the assistance anyway..

 

[bmc]

i took it as 2 metals of differing activity in a solution. i said iron deposit was formed on the more reactive mg and the concentration of fewhatever it was decreased whilst mg concentratoin increased if that makes sense

 

[Abtari]

for those who think that iron deposits on the magnesium strip, please provide a justification, much appreciated.

 

[Abtari]

Therefore what u woulda observed in the experiment would be the corrosion of magnesium, and a build up of iron on the nail.

i put down that in my answer,too.

 

[gogogadgetbrain]

for those who think that iron deposits on the magnesium strip, please provide a justification, much appreciated.

think about it this way, if you put a magnesium strip in a beaker of iron sulfate what would happen?- the magnesium would displace the iron ions in solution

it does this by giving up an electron (Mg -> Mg2+ + 2e-) this electron cant just swim through the water it it taken up by the iron ions in solution (Fe2+ + 2e- -> Fe) this reduction occurs on the surface of the magnesium and therefor iron deposits on the magnesium

this is the same for the cell in the diagram

-well thats what my couple of highschool chemistry years inclines me to believe

 

[jessd87]

It was stupid!

Well I too think that question was stupid.....and weird! It took me ages to try and work out what the hell was going on! your not the only one...but i wrote the same as you!

 

[bluebiro]

the question could have been interpretted a few ways....and it could have been worded better but hey shit happens

 

[missjelly_baby]

i don't know - i talked bout how it was like cathodic protection in that a more reactive metal (magnesium) will protect the less reactive (iron) against corrosion. therefore, magnesium was like sacrificial anode and it corroded where as iron did not. Like i said - i'm not sure but @ the tiem it seemed like the most correct thing to me.

 

[SilveryNightsky]

*reads answers
gdamnit i'm an idiot. Thank you thank you.

*kicks something.

 

[Haku]

i don't know - i talked bout how it was like cathodic protection in that a more reactive metal (magnesium) will protect the less reactive (iron) against corrosion. therefore, magnesium was like sacrificial anode and it corroded where as iron did not. Like i said - i'm not sure but @ the tiem it seemed like the most correct thing to me.

at the beginning of reading that question and saw it was 4 marks i thought that it would require something special.

so i wrote that Mg would produce a non porous oxide that would stop the corrosion, so nothing much happens. than i thought fuk it and went back to the normal displacement reactions. reading this, guess lucky that that i did,

 

[Captain Karl]

i don't know - i talked bout how it was like cathodic protection in that a more reactive metal (magnesium) will protect the less reactive (iron) against corrosion. therefore, magnesium was like sacrificial anode and it corroded where as iron did not. Like i said - i'm not sure but @ the tiem it seemed like the most correct thing to me.

I came to the same conclusion, and I'm pretty sure its the right one. I dont think it required any kind of genius thinking to work it out, it just required you to know that the reaction can happen in the one beaker. I'm glad i can find a few people to agree with on this one

 

[Touchstone]

If you didn't know how to answer THIS question, you didn't study properly. Oh and Yumi Cheeseman, I think I know you! Do you go to Gosford High?