Density and molar concentration

[mech-eng]

Hi,all.
a book(j.p holman,heat transfer 7e,chapter 11) gives
C (subindex)A = (ro) subindex A= P subindex A x M subindex A / Ro(universal) T

but another book(stanley middleman,an introduction to mass and heat transfer) gives
Ci=(ro)i/Mi. these are very different from each other.Ci is total molar concentration of
that species and ro is density that is mass concentration to be used in Fick's law.which one is true?

 

[Chestermiller]

Hi,all.
a book(j.p holman,heat transfer 7e,chapter 11) gives
C (subindex)A = (ro) subindex A= P subindex A x M subindex A / Ro(universal) T

but another book(stanley middleman,an introduction to mass and heat transfer) gives
Ci=(ro)i/Mi. these are very different from each other.Ci is total molar concentration of
that species and ro is density that is mass concentration to be used in Fick's law.which one is true?

The holman equation is for the mass density C_A of a species in an ideal gas if the species partial pressure is P_A. So ρo_A is the mass density.

In the middleman equation, ρ_i is the mass density of species i in a liquid or a gas, and C_i is the molar density of the species.