Physical Chemistry of Foods

Appendix G

Recalculation of Concentrations

Assume abinary mixtureof components 1 (solvent) and 2 (solute). The mass
fraction of the solute is given byc. Molar massMis given in daltons,ris
the density of the solution. We now have

Molar concentration (mol/L) m¼r

c

M 2

Molality (mol per kg water) m*¼

c

1 
c

?

103

M 2

¼

103 m

r
mM 2

Mole fraction x¼

c=M 2

ð 1 
cÞ=M 1 þc=M 2

If the system contains more solutes, the first equation will still hold for
Component 2, but not the other two equations.
For dispersed systems, the relations become far more complicated.
Moreover, in such systems part of the solvent may not be ‘‘available’’ for a
solute; see Section 8.3, item 2, ‘‘Nonsolvent water.’’