The apparent molal volumes, φv, of dilute aqueous MgCl2, CaCl2, SrCl2, and BaCl2 solutions have been determined at 1° intervals from 20 to 30° from precision density measurements. The apparent molal expansibilities, φE, have been calculated from the apparent molal volumes at various temperatures and have been equated to the infinite-dilution partial molal expansibilities (φE0 = Ē0). The Ē0's of the divalent chlorides increase in the order MgCl2 < CaCl2 < SrCl2 ≈ BaCl2. The Ē0's of these salts were divided into their ionic components, Ē0(ion), by assigning a value for Ē0(Cl-) = 0.046 ml/mol deg. The Ē0's of the divalent cations can be represented by the equation Ē0(ion) = -0.034(Z2/r) + 0.092 ml/mol deg. The Ē0's of the divalent cations and other monovalent cations and anions are discussed by dividing E0(ion) into the following components: Ē0(int), the intrinsic expansibility; Ē0(elect), the electrostriction expansibility; and Ē0(struct), the structural expansibility. The V̄0's and Ē0's of ions in solution are also qualitatively examined by describing the hydration of an ion by the Frank and Wen model.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry