calculating EMF's (2 Viewers)

[tina_goes_doo]

So...EMF ay?

 

[aim54x]

reverse the one with the SMALLER number, that means if ur numbers r 0.8 and -1.23, reverse the equation with the -1.23 value.

i understand this but i still mess up the anode and cathode

 

[tina_goes_doo]

Electrochemical cells are cool. It's the electrolytic cells that kill me!

Hey what name's better to use in the exam? Electrochemical or galvanic?

 

[Paroissien]

Galvanic from the syllabus

 

[lum]

yeah, my teacher told us she's only telling us it's also called electrochemical cells because we might need to know it for textbook questions, but for texts, galvanic is better, direct from sylabus.

but with the reversing sign of the smaller potential doesn't always work. i forgot what the question was, but in the answer, it was the negative of what i thought was the answer, would it be becuase it asked for the oxidation potential rather than the reduction potential?

 

[Slidey]

Uh... Galvanic cells are electrochemical cells.... and so are electrolytic cells.

"electrochemical" - chemical process which produces electricity.

but with the reversing sign of the smaller potential doesn't always work. i forgot what the question was, but in the answer, it was the negative of what i thought was the answer, would it be becuase it asked for the oxidation potential rather than the reduction potential?

If you are given a cell which doesn't even work in the first place, then that cell must necessarily have a negative EMF (or perhaps a 0 EMF)

It will work if you switch the LHS and the RHS, which effectively also switches the signs of your potentials (reduction becomes oxidation and vice versa), such that the absolute value of the EMF will be the same, but the total EMF is POSITIVE, with the cell actually working (displacement occurring).

If a question asks for oxidation potential, it will be the negative of what it is listed as being on the standard REDUCTION potentials table.

Oh, and I support speaking, writing and typing proper English.

 

[Xayma]

Uh... Galvanic cells are electrochemical cells.... and so are electrolytic cells.

"electrochemical" - chemical process which produces electricity.

Wrong. Electrochemical is a process involving electrochemistry. Which is related to electricity being created or converted from chemical activity.

Electrolytic cells actually require electricity.

 

[lum]

If you are given a cell which doesn't even work in the first place, then that cell must necessarily have a negative EMF (or perhaps a 0 EMF)

It will work if you switch the LHS and the RHS, which effectively also switches the signs of your potentials (reduction becomes oxidation and vice versa), such that the absolute value of the EMF will be the same, but the total EMF is POSITIVE, with the cell actually working (displacement occurring).

If a question asks for oxidation potential, it will be the negative of what it is listed as being on the standard REDUCTION potentials table.

Oh, and I support speaking, writing and typing proper English.

um, sorry, but if i switch the LHS and the RHS, how does that switch the signs of the potentials? the anode would still be the anode and cathode still cathode.

also, the EMF always has to be positive in a galvanic cell right?

 

[jamesy_1988]

just remember that the chart is the reduction potentails. so if you need the oxidation potentails you switch the sign around i.e. negative to positive.

Hope it helps

Jamesy