Limitations of Ellingham Diagram Chemistry Notes
Limitations of Ellingham Diagram :
There are two limitations which are as follow:
→ Kinetics of reaction and reduction : It is totally based on thermodynamic concept and it simply suggests whether the reduction of metal oxide is possible or not. It does not tell anything about the kinetics of the process ie, how fast the is reaction.
→ Reactant over product equilibrium : According to equation ∆G° = -RT In K, it is assumed that reactants and products are in equilibrium but it is not always true because the reactant/product may be solid. However, it explains how the reactions are sluggish when every species is in solid state and smooth when the ore melts down.
→ It is very interesting that the values of ∆H and ∆S° remain nearly constant every on varying temperature so the only dominant variable is T. The value of ∆S° depends upon the physical state of compounds as it is degree of randomness or disorderness. It increases as a compound melts (8 + I) as vaporises (1 g) because the molecular randomness increases on changing the phase from liquid to gas or solid to liquid.