What is the difference between electromotive force [EMF=E(reduction)+E(oxidation)] and E(cell)=E(cathode)-E(anode)? When do you use these formulas?
I am using Kaplan right now.Those two formulae mean the same thing. You can use either one since they are the same thing.
Recall that oxidation=anode and reduction=cathode.
EMF=Ecell
Ereduction=Ecathode
Eoxidation=-(Eanode)
What material are you studying from?
In a galvanic cell, Ecell is always greater than or equal to zero. When you use the formula, if you get a negative number then you either entered the wrong numbers or you assumed the reaction moved in the direction opposite to which it moves.I am using Kaplan right now. when using the above formulas, does E(oxidation)and E(reduction) have to be positive before you use the formula? In an electrolytic cell how do you determine whether lead (Pb) or copper (Cu) is being reduced?
Oxidation is loss of electrons, Reduction is a gain of electrons. At the anode (the site of oxidation) the neutral metal will be losing electrons and converting to the cation. At the cathode (the site of reduction) the metal ions in solution will be gaining electrons and attaching to the metal cathode. If this isn't enough, we'll need to know the half cell potentials for copper and lead to tell you more. In fact, if you can't get it from that, type all the information on the page about the cell just to make sure we have a complete picture.
cj8
No.The standard potential of lead is given as -0.127V and copper as +0.339V. Since copper has the higher standard potential it's being reduced. is this right? if lead head a standard potential of -0.400 then would lead be reduced?
No.
In an electrolytic cell at standard state, the side with the lower potential gets reduced. Electrolytic cells drive unfavorable reactions, so in the electrolytic cell you asked about, lead would be reduced.
If it were a galvanic cell, then copper would be reduced, but that is not what you asked about.
Changing lead's potential from -127V to -400V would not change which electrode experiences oxidation since it would still be a lower potential than copper.
Sorry I meant the question was for a galvanic cell.
So for a glavanic cell, the one which has the higher standard potential would be reduced and the one which has the lower standard potential would be oxidized.
For an electrolytic cell it would be the opposite. The one with the lower potential would be reduced and the one with the higher potential would be oxidized. Is that right?
Can you give me an example when the above would not be true?At standard state, yes this is true.
At other concentrations it might not be.
Can you give me an example when the above would not be true?