### Explaining 14.4 (Cell potential and gibbs)

Posted:

**Fri Feb 16, 2018 7:29 pm**Hello can someone please explain to me what I just read in simpler terms please (page 572):

"There is a hidden assumption in the derivation of Eq. 1. Maximum nonexpansion work is obtained when a cell is operating reversibly. Therefore, Eq. 1 applies only when the pushing power of the cell is balanced against an external matching source of potential. In practice, that means using a voltmeter with such a high resistance that the potential difference is measured without drawing any current. The potential difference under these conditions is the maximum potential that can be produced. It is called the cell potential (which is still widely called the electromotive force, emf, of the cell). From now on, Ecell will always be taken to represent this potential difference. A working cell, one actually producing current, such as the cell in a media player, will produce a potential difference smaller than that predicted by Eq. 1."

Thank you :)

"There is a hidden assumption in the derivation of Eq. 1. Maximum nonexpansion work is obtained when a cell is operating reversibly. Therefore, Eq. 1 applies only when the pushing power of the cell is balanced against an external matching source of potential. In practice, that means using a voltmeter with such a high resistance that the potential difference is measured without drawing any current. The potential difference under these conditions is the maximum potential that can be produced. It is called the cell potential (which is still widely called the electromotive force, emf, of the cell). From now on, Ecell will always be taken to represent this potential difference. A working cell, one actually producing current, such as the cell in a media player, will produce a potential difference smaller than that predicted by Eq. 1."

Thank you :)