Excess molar quantities of (a halogenated n-alkane + an n-alkane) A comparative study of mixtures containing either 1-chlorobutane or 1,4-dichlorobutane

Abstract

Excess molar volumes V m E at 298.15 K were obtained, as a function of mole fraction x, for series I: { x1-C 4H 9Cl + (1 − x) n-C l H 2 l + 2 }, and II: { x1,4-C 4H 8Cl 2 + (1 − x) n-C l H 2 l + 2 }, for l = 7, 10, and 14. 10, and 14. The instrument used was a vibrating-tube densimeter. For the same mixtures at the same temperature, a Picker flow calorimeter was used to measure excess molar heat capacities C p, m E at constant pressure. V m E is positive for all mixtures in series I: at x = 0.5, V m E/(cm 3 · mol −1) is 0.277 for l = 7, 0.388 for l = 10, and 0.411 for l = 14. For series II, V m E of { x1,4-C 4H 8Cl 2 + (1 − x) n-C 7H 16} is small and S-shaped, the maximum being situated at x max = 0.178 with V m E( x max)/(cm 3 · mvl −1) = 0.095, and the minimum is at x min = 0.772 with V m E( x min)/(cm 3 · mol −1) = −0.087. The excess volumes of the other mixtures are all positive and fairly large: at x = 0.5, V m E/(cm 3 · mol −1) is 0.458 for l = 10, and 0.771 for l = 14. The C p, m Es of series I are all negative and | C p, m E| increases with increasing l: at x = 0.5, C p, m E/(J · K −1 · mol −1) is −0.56 for l = 7, −1.39 for l = 10, and −3.12 for l = 14. Two minima are observed for C p, m E of { x1,4-C 4H 8Cl 2 + (1 − x) n-C 7H 16}. The more prominent minimum is situated at x′ min = 0.184 with C p, m E( x′ min)/(J · K −1 · mol −1) = −0.62, and the less prominent at x″ min = 0.703 with C p, m E( x″ min)/(J · K −1 · mol −1) = −0.29. Each of the remaining two mixtures ( l = 10 and 14) has a pronounced minimum at low mole fraction ( x min = 0.222 and 0.312, respectively) and a broad shoulder around x = 0.7.