Electro? (1 Viewer)

[Haku]

please anser the attached question. part ii)

 

[serge]

i think its like you said in the CO2 thread -.78

 

[Necros87]

well i think its a galvanic cell, maybe not... i havnt heard of it as spontanious before

b) *gets e^0 table out*
Fe2+(aq) + 2e --> Fe(s) -0.44V
Cu(s) --> Cu2+(aq) + 2e -0.34V (fliped round)
-----------------------------------------
Cu(s) +Fe2+(aq) --> Fe(s) + Cu2+(aq) -0.78 (electrons canceled)

therefore, the voltage required is 0.78V

 

[serge]

well i think its a galvanic cell

It looks like a galvanic cell (ie voltmetre)
but they tell you its acting as an electrolytic cell?

does electrolytic mean what i think it means?

 

[rnitya_25]

It is a galvanic cell because spontateous reactions generate heat and if electron transfer process occurs through external conduction, then electrical energy is generated. this is what happens in a galvanic cell....conversion of chemical to electrical energy.

as for part two: it is the emf/voltage required not voltage produced. so it must be electrode a - electrode b=

0.44 - 0.34 =0.1v

this is different to the other people's answers. idno, now i think im wrong, but this is what my teacher said.

 

[rnitya_25]

well i think its a galvanic cell, maybe not... i havnt heard of it as spontanious before

b) *gets e^0 table out*
Fe2+(aq) + 2e --> Fe(s) -0.44V
Cu(s) --> Cu2+(aq) + 2e -0.34V (fliped round)
-----------------------------------------
Cu(s) +Fe2+(aq) --> Fe(s) + Cu2+(aq) -0.78 (electrons canceled)

therefore, the voltage required is 0.78V

isnt Fe²⁺ supposed to be flipped around since it is the one on top, therefore the one being oxidised, therefore, having its half equation being flipped over?

i feel wierd now...

It looks like a galvanic cell (ie voltmetre)
but they tell you its acting as an electrolytic cell?

does electrolytic mean what i think it means?

what do you think it means?

 

[serge]

what do you think it means?

well i was hoping the 'but' would explain it

doesnt electrolytic mean you're adding a voltage to get a
non-spontaneous reaction happening?

yeh, i wikipediad it, i am right

 

[rnitya_25]

ok cool........im feeling wierd......nosadness, what is the answer?

 

[rama_v]

Yeah, what they want is for the reaction to go the other way
So if you in this instance instead of Iron oxidising you want copper to oxidise, and iron to reduce. So the reactions required are
Fe2+ + 2e- ->Fe(s) -0.44V
and Cu(s) -> Cu2+ + 2e- -0.34V

So you would need to pump 0.78 V into the cell to get teh reaction to go in the opposite direction, right??

 

[serge]

ok cool........im feeling wierd......

yeh the diagram doesnt help at all
adding a voltmeter for no reason?

its from the 2002 HSC

anyone with a 2003-2005 success book
should know the answer i think

Yeah, what they want is for the reaction to go the other way
So if you in this instance instead of Iron oxidising you want copper to oxidise, and iron to reduce. So the reactions required are
Fe2+ + 2e- ->Fe(s) -0.44V
and Cu(s) -> Cu2+ + 2e- -0.34V

So you would need to pump 0.78 V into the cell to get teh reaction to go in the opposite direction, right??

thats what i thought but i could be wrong
I think when you 'pump' it in the voltage still
counts as negative

 

[rama_v]

yeh the diagram doesnt help at all
adding a voltmeter for no reason?

its from the 2002 HSC

anyone with a 2003-2005 success book
should know the answer i think



thats what i thought but i could be wrong
I think when you 'pump' it in the voltage still
counts as negative

Yep, I've got success one right in front of me
It says "To operate the cell as an electrolytic cell the current would need to be reversed. It would take more than 0.78V in the opposite direction"

 

[serge]

Yep, I've got success one right in front of me
It says "To operate the cell as an electrolytic cell the current would need to be reversed. It would take more than 0.78V in the opposite direction"

yay, case closed
(now i can sleep tonight)

 

[rnitya_25]

ok.....so its adding the voltages together no matter if its cell potential or voltage required?......good god.

 

[Necros87]

one thing in chem i can do, if nothing else, is electrolitic and galvanic cells!

 

[rnitya_25]

and now i've just learnt something new from something that was wrong....thanks people...i would have gotten it wrong in the exam otherwise.

 

[Haku]

the way they did it is wrong in the successone book.

they flipped everything and still get a positive voltage...wtf.

but ur only suppose to flip the anode half equation and the emf. so it should both be minus. thus u get -0.78.

that means u need a voltage of 0.78 minimum to initiate the reaction.

 

[Necros87]

for electrolisis you need to get a negative answer

because the way they did the table, the voltages mentiond are voltages produced in a half equasion, so if you had to put a voltage across it, it would be giving of a negative voltage