Thermodynamics of (1‐Chloronaphthalene + n‐Alkane): Excess Enthalpies, Excess Volumes and Excess Heat Capacities

Abstract

AbstractA flow microcalorimeter of the Picker design has been used to measure molar excess enthalpies at 298.15 K of the seven binary liquid mixtures 1‐chloronaphthalene + n‐hexane, + n‐heptane, + n‐octane, + n‐decane, + n‐dodecane. + n‐pentadecane, and + n‐hexadecane. Experiments were performed in the discontinuous mode, covering essentially the whole composition range. The overall imprecision of the measurements is characterized by standard deviations from Redlich‐Kister type smoothing equations of generally less than ± 1 per cent of the maximum value HEmax of the excess enthalpy (with respect to mole fraction). The most striking feature is that for 6 ± n ± 16 (n denotes the number of C‐atoms of the n‐alkane) HEmax decreases with increasing n, the correlation being approximately linear. – For the mixtures 1‐chloronaphthalene + n‐hexane, + n‐heptane, + n‐octane, + n‐dodecane, + n‐pentadecane, and + n‐hexadecane molar excess volumes VE at 298.15 K were obtained, as a function of mole fraction, from measurements of the density with a vibrating‐tube densimeter. The excess volumes are negative in all cases and become less negative with increasing chain length of the n‐alkane. At equimolar composition, for (1‐C10H7Cl + n‐C6H14) we find VE = ‐1.555±10−6 m3 mol−1, and for (1‐C10H7Cl + n‐C16H34), VE = ‐0.397±10−6 m3 mol−1. A Picker flow calorimeter was used to determine molar excess heat capacities at constant pressure CEp at 298.15 K for all mixtures except for 1‐C10H7Cl + n‐C10H22, and + n‐C16H34. The excess heat capacity is essentially zero for the mixture with n‐hexane, and increases with increasing chain length up to (1‐C10H7Cl + n‐C12H26); for (1‐C10H7Cl + n‐C15H32), CpE is somewhat smaller, thus indicating a trend inversion.