Molar Isentropic Compressibility Research Articles

Molar conductance, viscosity and isentropic compressibility of some cobalt (III) complexes in organic solvents

Molar conductance, viscosity and isentropic compressibility of Bu 4NBPh 4, KX, (CH 3) 4NX, (C 2H 5) 4NX, (C 3H 7) 4NX, (C 4H 9) 4NX, (C 6H 5) 4PX, C 21H 38NX and C 19H 42NX (X = [ trans-Co(NH 3) 2(NO 2) 4] −) have been measured in acetonitrile (AN), n-butyronitrile ( n-BTN), propylene carbonate (PC) and N, N-dimethylacetamide (DMA). The conductance data have been analyzed by the Shedlovsky method to evaluate Λ 0 and K A, the viscosity data by Jones-Dole equation to evaluate viscosity B coefficients and the ultrasonic velocity data by suitable equations to get limiting apparent molal isentropic compressibility ( K s,ϕ 0) of the electrolytes. Most of these electrolytes show ion association in n-BTN and PC while they are completely dissociated in AN and DMA. The derived limiting parameters have been split into the ionic contributions using which radii ( r i) in solution, viscosity B ± coefficients and limiting ionic isentropic compressibility ( K s,ϕ 0) ± of various ions have been evaluated. The results of the present study show that (CH 3) 4N +, (C 2H 5) 4N + and K + are solvated in all these solvents by electrostatic interactions. (C 3H 7) 4N +, (C 4H 9) 4N +, (C 6H 5) 4B −,(C 6H 5) 4P +, C 21H 38N +, C 19H 42N + and [ trans-Co(NH 3) 2(NO 2) 4] − have large but almost constant respective ionic radii in each solvent except in PC which indicates no solvation of these ions by electrostatic interactions. Isentropic compressibility results on the other hand show that all these ions possess some special type of weak interaction with different solvents involving dispersive interactions. The extent of special interaction is larger in n-BTN and DMA as compared to that in AN and PC. Viscosity B ± coefficients also confirm the existence of some special type of interaction of the complex ions with the solvent molecules.

Ion-Solvent Interactions Investigated by Isentropic Compressibility Measurements of Tetraalkylammonium, Copper(I) and Sodium Salts in Binary Mixtures of Acetonitrile and n-Butyronitrile at 298.15 K

Ultrasonic velocities and densities of binary mixtures of acetonitrile (AN) and n-butyronitrile (n-BTN) with Bu4NBPh4, Bu4 NClO4, Bu4 NI, Bu4NBr, Pr4NBr, Et4NI, Et4NBPh4, NaBPh4, NaClO4 and CuClO4 have been measured in the concentration range 0.0045 - 0.2 mol kg−1 over the entire composition range at 298.15 K. Isentropic compressibilities (Ks) and apparent molal isentropic compressibilities (Ks,ø ) have been calculated. Limiting apparent molal isentropic compressibilities (Ko s,ø ) have been evaluated and split into the contribution of individual ions, i. e. into (Ko s,ø )± values. (Ko s,ø )± for Cu+, Na+ and Br− in all cases is negative and large, for Bu4N+ and Ph4B− positive and large, and for I− and ClO4 − negative only in AN, and becomes positive in binary mixtures of AN and n-BTN for all compositions. The negative (Ko s,ø )± values for Cu+, Na+ and Br− indicate strong ionsolvent interactions involving electrostatic ion-dipole interactions. The large and positive (Ko s,ø )± values for Bu4N+ and Ph4B− show some special type of ion-solvent interactions (hydrophobic or dispersion interactions) with AN and n-BTN. The small negative value changing to a small positive value for I− and ClO4 − indicates the change of a weak electrostatic ion-solvent interaction to another weak special interaction. A comparison of (Ko s,ø )± for Cu+ in some solvent systems shows that the ion-solvent interaction behaviour of Cu+ in AN+ n-BTN is similar to that in AN+ NM, AN+ TEP, BN+ TEP and PY + TEP mixtures but differs from that observed in AN+DMF and AN+DMSO mixtures.

Volumetric and acoustic properties of the ternary system (1-butanol+1,4-dioxane+cyclohexane)

Densities and speeds of sound for the ternary system 1-butanol+1,4-dioxane+cyclohexane have been measured at the temperatures of 298.15 and 313.15 K. Excess molar volumes and excess isentropic compressibilities have been calculated from experimental data and fitted by the Redlich-Kister equation for ternary mixtures. The ERAS model has been used to calculate excess molar volumes of the ternary mixture from parameters obtained from the constituent binary mixtures.

Influence of substitution in the aromatic ring on the behaviour of thermodynamic properties of pyrrolidin-2-one and aromatic hydrocarbons

The excess volume, V E and velocity of sound, u have been measured for the mixtures of pyrrolidin-2-one and aromatic hydrocarbons ( o-xylene, m-xylene, p-xylene and ethylbenzene) over the entire range of composition at 303.15 K. V E values are negative for all the mixtures and vary in the order: o-xylene>ethylbenzene> m-xylene> p-xylene. The results have been analysed by using the well-known Prigogine–Flory–Patterson theory. Molar isentropic compressibility K S and its excess values K S E have been obtained from the ultrasonic velocity data in combination with density values (calculated from excess volume). The K S E is negative for all the systems over the entire range of composition and vary in the order o-xylene> m-xylene>ethylbenzene> p-xylene. The partial and apparent quantities have also been estimated. The results are compared and discussed to gain insight into the interactions between the respective components.

Isentropic compressibilities of some copper(I), sodium(I) and tetraalkylammonium salts evaluated from ultrasonic velocity measurements in acetonitrile + N,N-dimethylformamide mixtures at 298.15 K

Ultrasonic velocity (u) and density (p) of tetrabutylammonium tetraphenylborate (Bu 4 NBPh 4 ), tetrabutylammonium perchlorate (Bu 4 NClO 4 ), copper(I) perchlorate tetraacetonitrile (CuClO 4 .4CH 3 CN), sodium perchlorate (NaClO 4 ) and sodium tetraphenylborate (NaBPh 4 ) have been measured at different salt concentrations in the concentration range 0.02-0.6 mol kg - 1 in binary mixtures of acetonitrile (AN) with N,N-dimethylformamide (DMF) containing 0, 10, 20, 40, 60, 75, 80, 90 and 100 mol % DMF. The isentropic compressibility (K s ) and apparent molal isentropic compressibility (K s , Φ ) of the salts in various solvent mixtures have been calculated. Limiting apparent molal isentropic compressibilities (K o s,Φ) for various salts have been evaluated and split into contributions of individual ions i.e. into (K o s,Φ) ′ values. The variation of (K o s,Φ) ′ values with solvent composition shows that Na + has very large negative (K o s,Φ) ′ values which show strong solvation of Na + in AN + DMF mixtures over the entire solvent composition range and the solvation of Na + by DMF is relatively stronger than that with AN. Cu + also shows strong but relatively less solvation as compared to Na + in AN + DMF mixtures over the entire solvent composition range. The solvation of Cu + by AN is relatively stronger than with DMF. ClO - 4 shows much weaker solvation in AN+DMF mixtures by having some interaction with AN in the AN rich region of the mixture.

Conductivities, Partial Molar Volumes, and Isentropic Compressibilities of Sodium, Potassium and Ammonium Thiocyanates in Water + N,N-Dimethylformamide Mixtures at 20°C

Abstract Conductance, ultrasonic velocity, and density measurements are reported for NaSCN, KSCN and NH4SCN in water, N,N-dimethylformamide (DMF), and water + DMF mixtures at 20°C. The limiting molar conductances and association constants have been derived from the Lee–Wheaton conductivity equation. The single-ion conductances have been evaluated using Bu4NBPh4 as the “reference electrolyte”. The limiting molar volumes and apparent isentropic compressibilities have been calculated. The ion–ion and ion–solvent interactions have been discussed.

Densities and Speeds of Sound of the Ternary Mixture 2-Butanol Plus 1-Chlorobutane Plus Tetrahydrofuran

Experimental densities (ρ) and speeds of sound (u) were obtained for the ternary system (2-butanol + 1-chlorobutane + tetrahydrofuran) at three temperatures: 283.15, 298.15 and 313.15 K. Excess molar volumes (V E ) and isentropic compressibility deviations (Δκ S ) have been calculated from experimental data. A discussion of the thermodynamic behavior of the ternary system in terms of molecular interactions and structural and packing effects is presented.

Compressibility studies of some copper (I) and tetraalkylammonium salts in binary mixtures of triethylphosphite with acetronitrile, benzonitrile and pyridine at 298.15 K

Ultrasonic velocity (u) and density (ϱ) of tetrabenzonitrile copper (I) perchlorate (CuClO 44C 6H 5CN), tetrabutylammonium tetraphenylborate (Bu 4NBPh 4) and tetrabutylammonium perchlorate (Bu 4NClO 4) have been measured at different salt concentrations in the concentration range 0.002–0.28 mol kg −1 in binary mixtures of triethylphosphite (TEP) with acetonitrile (AN), benzonitrile (BN) and pyridine (PY) containing 0, 20, 40, 60 and 80 mol % TEP. The isentropic compressibility (K s) and apparent molal isentropic compressibility (K s,ø) in various solvent systems have been calculated. Limiting apparent molal isentropic compressibilities (K 0 s,φ for various salts have been evaluated and split into contributions of individual ions i.e. into (K 0 s,φ) ± values. The variation of (K 0 s,φ) ± values with solvent composition shows that Cu + indicates strong solvation in AN + TEP, BN + TEP and PY + TEP mixtures over the entire solvent composition range and the solvation with TEP is relatively stronger than that with AN, BN and PY. ClO 4 − is better solvated in AN + TEP mixture by having some interaction with AN but is poorly solvated in BN + TEP and PY + TEP mixtures. Both Bu 4N + and Ph 4B − show some interaction with TEP in the TEP-rich region of all the solvent systems.

Complex formation between alkane-α, ω-diols and cyclodextrins studied by partial molar volume and compressibility measurements

The binding of a series of alkane-α,ω-diols, HO(CH2)nOH, n = 4 to 7, to α- and β-cyclodextrin (CD) has been studied by measurements of partial molar volumes (PMVs) and isentropic partial molar compressibilities (PMCs) at 25°C. From the PMV and PMC data, changes in the partial molar quantities upon going from a free state in aqueous solution to a complexed state were evaluated for the diols. Negative changes in PMV and PMC were observed for complex formation with α-CD, while positive values were obtained for the β-CD complexes. Equilibrium constants for the different complexes, assuming the formation of 1:1 complexes, were evaluated from the PMV and/or PMC data, and were found to increase with increasing chain length of the included diol for both α- and β-CD complexes. The equilibrium constant for complex formation is generally higher for the β-CD than for the α-CD complexes.

Volumetric and Acoustic Properties of the Ternary Mixture 1-Butanol+1-Chlorobutane+Tetrahydrofuran at 283.15, 298.15, and 313.15 K

Experimental densities (ρ) and speeds of sound (u) were obtained for the ternary system (1-butanol+1-chlorobutane+tetrahydrofuran) at three temperatures: 283.15, 298.15, and 313.15 K. Excess molar volumes (V E ) and isentropic compressibility deviations (Δκ S ) have been calculated from experimental data. A discussion of the thermodynamic behavior of the ternary system with temperature variation is presented.

Thermodynamic investigation of surfactant aggregation in 2-pyrrolidinone

The partial molal volume ( V φ,s) of several surfactants viz. sodium dodecylsulphate (SDS) and sodium tetradecylsulfate (STS), tetraethylammonium bromide (Tea-Br), Span-80, 60, 40, 20 in 2-pyrrolidinone have been determined at concentration below 0.80 mol kg −1 at 30 and 40 °C. The partial molal isentropic compressibility ( K φ,s) of micellar solutions of surfactants SDS, STS, Span-80, 60, 40, 20 have been calculated from ultrasonic velocity measurements at 30 °C. The infinite dilution values of V φ,s and K φ,s of the solubilizates in 2-pyrrolidinone are also estimated. The critical micellization concentration (cmc) values for the systems are taken at a concentration where a clear and well defined break is observed in the concentration dependence of the ultrasonic velocity. The cmc data has been utilized to compute standard free energy of micellization (Δ G m o). The results have been interpreted in terms of transfer of surfactant monomer from dispersed to aggregated state. Limiting parameters have been used to explain the solvation of surfactant molecules.

Volume and compressibility of mixtures of γ-butyrolactam ( n = 5) with nitro-compounds

Excess volume and ultrasonic velocity measurements have been carried out for nitromethane (NM), nitroethane (NE), 1-nitropropane (1-NP), 2-nitropropane (2-NP) and nitrobenzene (NB) in γ-butyrolactam ( n=5), i.e. pyrrolidin-2-one (PY) at 303.15 K over the entire composition range. The V E values are negative for PY+nitroalkanes expect for NM which exhibits S-shaped behaviour. A very small V E is observed in PY+NB. Using ultrasonic velocity and excess volume data, molar isentropic compressibility K S and excess isentropic compressibility K S E have been computed. The results have been analysed in the following sequence. (1) Quantitative estimation of different contributions, viz. interactional, free volume and P ∗ effect to V E using Prigogine–Flory–Patterson (PFP) theory; (2) the calculation of partial molar volumes, apparent molar compressibility and their excess values to gain insight into solute–solvent interactions.

Concentration and temperature dependence of ultrasonic velocity and isentropic compressibility in aqueous sodium nitrate and sodium thiosulfate solutions

N. Rohman and S. Mahiuddin, J. Chem. Soc., Faraday Trans., 1997, 93, 2053 DOI: 10.1039/A700022G

Speeds of sound and isentropic compressibilities of { xH(CH 2) νO(CH 2) 2O(CH 2) 2OH +(1 − x)H 2O}, ( ν= 1, 2, and 4) at the temperature 298.15 K

The speeds of sound in { xH(CH 2), O(CH 2) 2O(CH 2) 2OH + (1 − x)H 2O} for v= 1, 2 and 4 have been measured over the whole range of xat the temperature T= 298.15 K. The molar isentropic compressibilities K S,mof these solutions were estimated from the products of the molar volume and the isentropic compressibility κ s, and the excess values K S,m Ewere also calculated. The behaviour of the K S,m Ecurves for the series of mixtures is similar to that found previously for their excess molar volumes. Also, the deviations of the speeds of sound u Dhas been defined and calculated for all measured values of x. These values were compared with the mixing function δ ucalculated in the literature. The behaviour of u D, δ u, and K S,m Ewith composition and the number of carbon atoms in the aliphatic chain of the alkoxyethanol is discussed.

Transport and compressibility studies of some copper(I) perchlorates in binary mixtures of benzonitrile and acetonitrile

Transference numbers of ClO–4 and Cu+ ions in copper(I) perchlorate have been measured in the concentration range 0.02–0.22 mol dm–3 in benzonitrile(BN)–acetonitrile(AN) mixtures at 298 K by the modified Hittorf method. The limiting transference numbers of Cu+(to+Cu) in various solvent systems were evaluated by the modified Longsworth method. Molar conductances, ultrasonic velocities and densities of CuClO4· 4CH3CN and [Cu(DMPhen)2]ClO4 were measured at 298 K in BN–AN mixtures. The limiting molar conductances (Λo) of the electrolytes were obtained by analysis of the conductance data using the Shedlovsky equation. Limiting ionic conductances (λoi) for Cu+, [Cu(DMPhen)2]+ and ClO––4 ions and hence their solvated radii (ri) were calculated. The variation in solvated radii of ions as a function of solvent composition showed no preferential solvation of any ion by AN or BN. From the ultrasonic velocity and density measurements, the isentropic compressibilities (κs) and the limiting apparent molal isentropic compressibilities (κoϕ) for CuClO4· 4CH3CN and [Cu(DMPhen)2] ClO4 were evaluated. That κoϕ values for the copper(I) salts became less negative or more positive with increasing BN mole fraction indicating that both these copper(I) salts are structure makers in AN and that the structure-making tendency of the salts decreased with increasing BN mole fraction.

Excess molar volumes, speeds of sound, and isentropic compressibilities of binary mixtures of furfural with some aliphatic alcohols

Excess molar volumes and isentropic compressibilities for the binary mixtures of furfural with methanol, ethanol, 1 -propanol, 2-propanol, 1-butanol, and 2-butanol have been computed from the experimentally measured densities and sound speeds at 308.15 K over the entire composition range. All the systems studied exhibit contraction on mixing. The results have been discussed in terms of the specific interactions between the component molecules of the binary mixtures. Keywords: excess molar volumes, isentropic compressibilities, furfural, aliphatic alcohols, unlike reactions.

ChemInform Abstract: Structural Effects in the Partial Molar Volumes and Isentropic Compressibilities of Organic Bases and Their Conjugate Ions

Abstract Partial-molar-volume and isentropic-compressibility measurements in water are reported for a systematically chosen series of organic N-bases and their conjugate Bronsted-acid ions so as to investigate the role of the structures of these molecules in their interactions with the water solvent in the ionized and un-ionized states. The results also give the changes of volume and isentropic compressibility upon ionization, hence information on solvent electrostriction due to ionization. The electrostriction effect is related to the entropy of ionization in cases where suitable reliable information exists. The molecular structures are mainly aromatic and saturated heterocycles with one or two N atoms in the ring, or rings with an N and an O atom. Comparisons are also made with a “linear” N-base, ethylenediamine. The results for these various molecules enable the volumetric effects of the following molecular structure changes to be accurately evaluated: effect of one or two N atoms in a ring; effect of CH 2 ·CH 2  bridging with respect to hydrophobicity; effect of replacement of O by N and by CH 2  and of N by CH, or NH by CH 2  in a ring; introduction of aromaticity; position of N atoms in isomeric heterocyclic structures; and number of CH 2  groups in a ring. The results from this series of comparisons enable some conclusions to be reached regarding additivity of “group contributions” and the role of structural specificity in the volumetric properties of organic bases and their cations in aqueous solution.

Heat capacities and isentropic compressibilities of electrolytes in propylene carbonate at 25 °C

The heat capacities per unit volume and sound velocities of many solutions of 1:1 electrolytes in propylene carbonate (PC) were measured at 25 °C. Combining these data with previously published densities, apparent molar heat capacities and isentropic compressibilities were calculated. By extrapolation to infinite dilution, the corresponding standard partial molar quantities were obtained. The heat capacities and compressibilities of water in PC were also calculated. Through ionic additivity, it was possible to calculate these functions for all alkali and tetraalkylammonium halides. The magnitude and trends with ionic size of the heat capacities of electrolytes in PC are similar to those in other aprotic solvents such as acetonitrile (ACN) and dimethylformamide (DMF) and significantly different from those in water. On the other hand, with compressibilities, the magnitudes sssssssare the same in PC and in water for alkali halides but significantly different for tetraalkylammonium halides. The trends with ionic size are similar to those in ACN. These effects can be interpreted through ion–solvent interactions. The separation of these thermodynamic functions into their ionic contributions is also discussed.

Changes in partial molar volume and isentropic partial molar compressibility of self-association of purine and caffeine in aqueous solution at 1?1600 bar

Ultrasound measurements of purine and caffeine in aqueous solution as function of pressure are reported at 25°C and used to calculate the changes in their partial molar volumes and partial molar compressibilities due to self-association. The effect of pressure is to increase the association. The volume changes are negative for the self-association process, becoming less negative with increasing pressure. This is caused by the monomer in the associated state. The partial molar volume of the monomer in the associated state increases with pressure, contrary to what is expected for nonelectrolytes in water. Hydration of the associated monomer must be a key to this increase. The result suggest that dipole-induced dipole interactions is a possible mechanism for the association process and not hydrophobic interactions. The change in the partial molar compressibility of the association is positive, decreasing with increasing pressure.

Effect of geometry on the thermodynamic properties of micellar systems: trialkylamine oxides in water

The apparent molar volumes, heat capacities, relative enthalpies, and isentropic compressibilities of symmetrical trialkylamine oxides and cyclohexyldimethylamine oxide were measured in water at 25 °C. The data were in most cases analyzed with a mass-action model which was previously developed (J. Phys. Chem. 87, 1397 (1983)) for micellar systems. Trimethylamine oxide shows no sign of micellization while the three next members of this homologous series and cyclohexyldimethylamine oxide form aggregates with relatively low aggregation numbers. The thermodynamic data were compared with those of assymmetrical amine oxides to investigate the effect of geometry on the micellar properties. The thermodynamic properties of the solutes in the pre-micellar region show a very good group additivity which is independent of geometry. On the other hand, with symmetrical isomers, the CMCs are much larger, the aggregation numbers smaller and the thermodynamic functions of micellization larger. These geometrical factors can be taken advantage of for thermal energy storage.