A Molality-Molarity Paradox? Consider w grams of a salute of molecular weight p dissolved in W grams of a solvent to form a solution of density d grams per ml. Then the molelity m = 1000wlpW and the molarity M = 1n n n d hrd, w .. L, -,. Suppose we have a solution such that the molality equals the molarity. I t then follows that w = W(d - 1). It is possible, a t least in principle, form to be equal to M in a nonqueous solution where d is ereater than unitv. urovidina oomuonents with suitable partial molar volumes are chosen. he case whew d itpp&ches un& corresponds to a very dilute aqueous solution when m approaches M. An impossible situation develops, however, when d is less than unity; ,yet there seems no obvious reason why m could not equal M in a solution for which dis less than unlty. A"""--,
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(See page 248)
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Journol o f Chemicol Fducotion
Molality-Molarity Paradox-A
Second Look
(Continued from page 830) The situation arises by imposing too many restmink on the system. If we write the relationship between m and A4 in the form
it is clearly impossible for m to equal M and simultaneously ford to he less than unity.
SIDNEYTOBY Rutgem University New Bnmswick, N . J .
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Journal of Chemical Education
