We have already commented that equilibrium electrochemistry allows us to estimate thermodynamic properties such as rGo very accurately. The same quantities can be obtained from “ thermal ” measurements such as the free energies and enthalpies of formation and standard entropies of substances wherein an error of about 0.5 % can not be ruled out. But emfs can be measured to an accuracy of better than 0.0001V.
The temperature dependence of emf can be measured by keeping the galvanic cells in suitable thermostats, allowing for proper equilibration, and then measuring the cell potentials in suitable ranges of temperature.
The rate of change of emf E with temperature T, dE / dT is related to dG / dT as follows
d ( rG ) / dT = -n F (d / d T)
(22.11)
But since d ( r G ) / d T = - S (See problem 21.7, Chapter 21 ), we have
( r S = n F (d / d T)
(22.12)
and knowing r S and rG, r H can be calculated through
rGo very accurately. The same quantities can be obtained from “ thermal ” measurements such as the free energies and enthalpies of formation and standard entropies of substances wherein an error of about 0.5 % can not be ruled out. But emfs can be measured to an accuracy of better than 0.0001V. 
/ d T) 
