Criticisms
Athel Cornish-Bowden has argued enthalpy-entropy is probably a statistical artifact, which could result in observing a relationship between two variables which may at first seem to be trustworthy, but is false because the relationship being observed does not actually exist. Sometimes a graph that is plotted against temperature will be used to attain a value of enthalpy and entropy, when in fact this is not the proper way to measure these values. Assume a linear, Arrhenius plot of the natural log of the rate constant, ln(k), versus inverse temperature T−1. Both the intercept and slope of this plot are used alongside transition-state theory to reveal a linear plot of ΔS‡ versus ΔH‡. This approach is fine for ΔH‡. On the other hand, the ΔS‡ value is derived from an extrapolation that can be as high as twenty times the range of the measured data. One cannot hope for more than a broad idea of the true value of ΔS‡.
Plots of ΔH‡ vs. ΔS‡ have been shown to exhibit an extremely strong linear relationship. Criticism of the enthalpy-entropy compensation arises from this strong correlation, which is “too good to be true.” It is believed these plots are a result of looking at the same variable in two different ways, and nothing experimentally significant is being shown.
Ideally, calorimetry experiments can yield the proper measurements of enthalpy and entropy.
Read more about this topic: Enthalpy-entropy Compensation
Famous quotes containing the word criticisms:
“The sway of alcohol over mankind is unquestionably due to its power to stimulate the mystical faculties of human nature, usually crushed to earth by the cold facts and dry criticisms of the sober hour. Sobriety diminishes, discriminates, and says no; drunkenness expands, unites, and says yes.”
—William James (1842–1910)
“I have no concern with any economic criticisms of the communist system; I cannot enquire into whether the abolition of private property is expedient or advantageous. But I am able to recognize that the psychological premises on which the system is based are an untenable illusion. In abolishing private property we deprive the human love of aggression of one of its instruments ... but we have in no way altered the differences in power and influence which are misused by aggressiveness.”
—Sigmund Freud (1856–1939)