Abstract
AbstractAn equation of state has been obtained for a pure n‐alkane liquid with correlations of molecular orientations (CMO). CMO is simulated by considering small densely packed and loosely packed regions randomly dispersed throughout the liquid. These differ by the presence of holes in the loosely packed regions. The relevant parameter for CMO is the fraction of dense‐packed regions p in the pure n‐alkane. The fraction p decreases rapidly with increase of temperature and increases with pressure. It is found that CMO has a short range segmental rather than molecular character. The model correctly predicts the decrease in energy, entropy and volume brought about by the presence of CMO in the pure liquid. Parameters of the theory are fitted to HE(T) and HE(P) for n‐C12 and the following order contributions to mixing quantities are predicted: dVE/dT, dVE/dP, Δ(γVT), ΔCv and Δ(αγ VT) where α and γ are the thermal expansion and thermal pressure coefficients. Good qualitative and quantitative agreement is found with experiment.
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