Question

Electrode potentials

Ok so I have a fundamental doubt

a) If i take copper in copper sulfate solution what is going to happen?
As i see, copper has a +0.34V reduction potential .
What that tells me is that Cu 2+ ions would really LOVE to eat up 2 electrons and become Cu atoms. In doing so , they end up have Lower energy state, thus releasing energy, and the energy released per coulomb is 0.34 Joules. Is this correct? I hope so, cause this makes a lot of sense to me

Answer 1

, cause really when i have a positive and a negative charge far apart, nature tries to bring them together, and overall potential energy decreases, and energy gets converted into kinetic energy (yea i am really into physics.. :P)

ok Now lets talk about zinc

Zinc has a reduction potential of -0.76V. Which tells me, zinc would RATHER get oxidized .. cause apparently if Zn --> Zn+2 + 2e-, energy of 0.76 joules per coulomb is released,
Now why is this?!

i do understand Zn would obtain OCTET structure if it lost 2 electrons, but, hey, to remove 2 electrons from zinc you would atleast require some energy right?!
:-/

@Somy @KL-RC @Vincent-Lyon.Fr

Answer 2

oh wait.. these potentials are actually measure with reference to SHE right?.. and basically its COMPARED TO SHE right?..

in reality absolute potentials (if we COULD MEASURE SOMEHOW) would be positive for all? right? xD

Answer 3

yes we measure it relative to standard hydrogen electrode potential which we take it as zero, that does not mean 0 energy is needed to to remove electron from hydrogen?

Answer 4

Is this the same question you asked me last night?

Answer 5

u guys are sitting for A2?

Answer 6

Ok yea i get it.. so like i said, if we could REALLY measure the ABSOLUTE potential.. (maybe considering infinity as zero instead of considering hydrogen as zero.. just theoretical )
then all the reduction potentials would be +ve right?

Answer 7

@KL-RC yes!.. but i didn't compose it properly :P

Answer 8

ur right :) but why should u say this r "all the eduction potentials would be +ve right"

Answer 9

Ok when I read your last 2 lines Me and Somy are thinking the something which is Orbitals

Answer 10

@chmvijay cause.. ultimately, YOU SHOULD need some energy to seperate electrons from an atom.. :P ?

Answer 11

But it has s Orbitals which is having 2 electrons so means electron can easily be lost due to spin pair repulsion

Answer 12

@Mashy we are not A levels sadly so i dunno it

Answer 13

but then again you said 2 so....

Answer 14

@thushananth01 m actually a physics teacher :P..

@KL-RC whatever happens, i believe you would need energy to remove electron from an atom (neutral atom)

Answer 15

really?

Answer 16

@thushananth01 yea.. but my electrochemistry is a little rusty!

Answer 17

hehe, which means ur a genius at physics i suppose ;)

Answer 18

when u dip cu metal into the copper solution its not exactly going to eat two electrons :) unless u connect another end of the electrodes to zinc (for example). otherwise there is small -v charges on the copper metal surface and ions interacting with the copper metal will have +ve charge as result potential is developed between them :)

Answer 19

that's exactly what I was telling you Mash :) remember?

Answer 20

but unfortunately there IS no 2nd electrode :(

Answer 21

@thushananth01 NO not really :P

@chmvijay yes yes.. that is cause, those cu2+ ions need 2 electrons.. and somehow i have to PROVIDE that electron.. and for that i need another electrode.. yea i get that!

Answer 22

@KL-RC well i was really confused, until i thought mroe abou tit :P

Answer 23

what is @somy typing? :O

Answer 24

LOL I have no idea ^^'

Answer 25

if u have any other problem in the electro-chemistry :) refer advanced chemistry by Phillip Matthew :) nice book :)

Answer 26

@chmvijay
thanks man!.. i will :) :)!!

Answer 27

Apparently Somy is drawing

Answer 28

@Mashy " the more (or less positive) the electrode potential, the more difficult it is to reduce the ions on the left. So the metal on the right is relatively reactive and is a relatively good reducing agent. "

Answer 29

its written in the book

Answer 30

@Somy my left or ur left? xD

Answer 31

Zn2+ (aq) 2e- (equilibrium sign) Zn(s) voltage = - 0.76

Answer 32

@Somy
yes yes.. i get it !!!

Answer 33

Yo Mashy?

Answer 34

@yes KL!

Answer 35

can you explain me? xD

Answer 36

@Mashy i wonder what you are getting and is it your answer?

Answer 37

@somy my original question was

why "Zn2+ (aq) 2e- (equilibrium sign) Zn(s) voltage = - 0.76" that reaction has a NEGATIVE potential.. cause, a negative potential indicates, that the reaction is not really all that favorable, or it indicates that energy has to be supplied to carry that reaction, and i was wondering why that is so? cause, clearly a positive and negative would love to react .. so i would expect that reaction to have a positive potential .. that was my original question.. :)

Answer 38

@Mashy sorry im stupid atm :P

Answer 39

no no.. chill :P

Answer 40

i got it!!

Answer 41

@Mashy on the sofa?

Answer 42

Ok lets stop idle talk here

cause it ll disturb all the other wonderful people who answered this question.. :P

------CLOSE ------

Answer 43

energy has to be supplied to carry that reaction? its not delta H is just indication -ve and +ve are potentials and not enthalapy :)

Answer 44

its the same as enthalpy.. but in different units, enthalpy is in joules

this is joules per coulomb

but the negative sign only says, that its harder for zinc to reduce COMPARED TO HYDROGEN.. xD. maybe m not able to explain this.. but i get it thanks to you guys :D :D!!

Answer 45

@Mashy i thought u just closed it =_=

Answer 46

yes yes.. CLOSED!!!!!!!!!!!!!!!!!!!

Answer 47

I think it could be due to reactivity? maybe?

Answer 48

or like Somy said it is because it's a exothermic reaction

Answer 49

@Mashy
I would not add anything to the discussion. The answers given seem really great.
You can actually close this question. ;-)