Mole Fraction—Molality Conversion for Henryan Activity Coefficients

Mole Fraction—Molality Conversion for Henryan Activity Coefficients 

The relationship between Henryan coefficients measured on the two concentration scales can be derived as follows. Consider an aqueous solute having a mole fraction X and a molality m. Because the chemical potential of this solute is the same whether we measure concentrations in mole fractions or molalities, we write 

For all but large values of m, the difference between 7// and 7/f is quite small, and the conversion is often neglected. Nevertheless activity coefficients based on mole fractions are generally more coherent with the rest of thermodynamics, and are to be preferred in situations where the choice makes any difference. 

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