Cell Potential, Electrical Work & Free Energy Video Lecture | Additional Study Material for Class 12

this is doctor Hayek and this video is
about electrochemistry today we will
talk about the relationship between the
cell potential electrical work and free
energy check my previous video on how to
calculate the standard cell reduction
potential I will post a link in the
description below today we will explore
the relationship between thermodynamics
and electrochemistry the work that can
be accomplished when electrons are
transferred through a wire depends on
the thermodynamic driving force this
driving force is defined in terms of
potential difference between two points
on the circuit and therefore the
electro-motive force is going to be
equal to the potential energy which is
equal to a Joule of work for a Coulomb
of charge
now here we'll consider the cell as the
system and since the work is done by the
cell it will be indicated by a negative
sign and therefore the potential energy
is going to be equal to minus W over Q
if we rearrange this expression we will
get that the work is equal to minus Q
multiplied by e max from this equation
it could be seen that the maximum work
that could be obtained at the maximum
cell potential and therefore W max is
equal to minus Q E max it's not worthy
to mention that we can never realize the
maximum work from a cell because of the
wasted energy through frictional heating
when a current flows however we can
measure the maximum cell potential using
an efficient digital voltmeter the
charge can be calculated by knowing the
amount of electrons or number of mole of
electrons passing through the wire and
using Faraday's constant and therefore Q
is equal to number of more electrons
multiplied by for a day's constant for
these law states that the charge of one
more electron is equal to ninety six
thousand four hundred eighty five
coulombs and therefore we have what we
call F which is the Faraday's constant
it's equal to 96 thousand four
hundred eighty-five coulombs per mole
electron and now we can relate the
potential of a galvanic cell to the free
energy we know that full process at
constant temperature and pressure the
change on free energy is equal to the
maximum of useful work and therefore
Delta G is equal to the work maximum and
we know that the work maximum is equal
to minus Q times the cell potential and
we know that Q is equal to number of
mole electrons multiplied by Faraday's
law so if we put all this together we
will have to the change of free energy
it's equal to minus number of mol
electrons multiplied by for a dis
constant multiplied by the maximum at
cell potential for standard conditions
Delta g0 is going to be equal to
negative number of mol electrons
multiplied by Faraday's constant
multiplied by the standard cell
potential now we know that for
spontaneous processes Delta G has to be
negative and since Delta G from this
expression is proportional to the
negative of cell potential so we can
tell that the galvanic cell will always
run in the direction that gives positive
cell potential I hope these videos help
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