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[profitis]

@mark E no.the nernst equation simply relates voltage to concentration or more precisely,activity of all participating species in an electrode half-reaction.it says nothing about reversability,the kelvin statement is all about reversability.the kelvin statement implies that every time you go through a thermodynamic cycle that you must put effort in the system to repeat it.there is no net change in a karpen cell over time that correlates in any way with the energy it gives because it doesnt need to abide by kelvin statement to fulfill its thermodynamic entropy requirements. 

[sarkeizen]

@sarkeizen so you want me to CITE and EXPLAIN in order to FORCE spontaneously reversable thermodynamics in a concentration cell that dont change over time correct?

Your statement is too ambiguous.  Your argument needs to be a series of statements which force a conclusion (Therefore textbooks necessitate the existence of and ability to build a battery which can run an ipod like device constantly and eternally.).  To force, in this case means demonstrate there exists no logically-valid alternative.

Stepping in here for a moment, my understanding of the Nernst equation is that entropy is implicit within it.

If so, that kind of illustrates my much earlier comment about profitis being a little ignorant about how physical formulae are developed.  Physical formulae are empirical truths, so if we use a regression analysis (or some other tool) to create a formula to relate property X and Y.  We include all the assumptions involved in observing property X and Y.  This creates limitations on inference.  Occasionally math does reveal things that we didn't observe.  The Dirac equation, for example predicted positrons.  However this is not necessarily the general case.

[profitis]

yes demonstrate is the key word @sarkeizen i.e. to build and see however textbooks will have to do because you are there and i am here so again,do you want me to CITE and EXPLAIN (your not an electrochemist i presume) how a concentration cell,s entropy requirements can be met without kelvin rule in the picture,yes or no. 

[profitis]

@sarkeizen your implying that kelvin statement is necessary for all thermodynamic entropy requirements is totaly false.

[MarkE]

@mark E no.the nernst equation simply relates voltage to concentration or more precisely,activity of all participating species in an electrode half-reaction.it says nothing about reversability,the kelvin statement is all about reversability.the kelvin statement implies that every time you go through a thermodynamic cycle that you must put effort in the system to repeat it.there is no net change in a karpen cell over time that correlates in any way with the energy it gives because it doesnt need to abide by kelvin statement to fulfill its thermodynamic entropy requirements.

Thanks, but if I let two half cells communicate that have different concentrations of the same ions, my understanding is that they will each move towards the equilibrium concentration.  If they were thermodynamically reversible they might move towards or away from the equilibrium concentration.  Do I understand that incorrectly?