Excess enthalpies and excess volumes of nitromethane +, and nitroethane + each of several non-polar liquids

Abstract

Excess molar enthalpies H m E and excess molar volumes V m E have been measured for xCH 3NO 2 + (1− x) c-C 6H 12 at 298.15 and 318.15 K; +(1− x)C 6H 14 at 298.15 K; +(1− x)(CH 3) 2CHCH(CH 3) 2 ( H m E only) at 318.15 K; +(1− x)CCl 4 at 298.15 and 318.15 K; +(1− x)C 6H 6 at 298.15 K; +(1− x) p-C 6H 4(CH 3) 2 at 298.15 and ( H m E only) 318.15 K; and for xC 2H 5NO 2 + (1− x) c-C 6H 12 at ( H m E only) 298.15 K and 318.15 K; +(1− x)CCl 4 at 298.15 and 318.15 K; +(1− x)C 6H 6 at 298.15 K; and +(1− x) p-C 6H 4(CH 3) 2 at 298.15 K. The H m E's were determined with an isothermal dilution calorimeter and the V m E's with a continuous-dilution dilatometer. Nitromethane + cyclohexane, + n-hexane, and + 2,3-dimethylbutane are only partially miscible. Particular attention was paid to the dilute region. The limiting partial molar enthalpies of dilution of CH 3NO 2 in the three alkanes are between 15 and 17 kJ·mol −1 and the limiting partial molar enthalpies of dilution of the three alkanes in CH 3NO 2 lie between 12.8 and 14.5 kJ·mol −1. The excess partial molar volumes of CH 3NO 2 in an alkane are large and positive, ranging from 6.4 to 8.5 cm 3·mol −1. For the completely miscible mixtures, H m E decreases in the order CCl 4 > p-C 6H 4(CH 3) 2 > C 6H 6; while V m E for these three mixtures has approximately the same magnitude, but shows considerably different composition dependence depending upon the solvent. All the mixtures with nitroethane are completely miscible. In general, H m E is large and positive for mixtures with c-C 6H 12 and becomes less positive in the order CCl 4 > p-C 6H 4(CH 3) 2 > C 6H 6. V m E is large and positive for mixtures with c-C 6H 12 and S-shaped for mixtures with CCl 4 with negative values in the nitroethane-rich region. For mixtures with C 6H 6 and with (CH 3) 2CHCH(CH 3) 2 V m E is S-shaped with positive values in the nitroethane-rich region.