Conductance, Dissociation Constant and Thermodynamic Parameters Studies of Succinic acid in Water + Pyruvate Carboxylase and Water + Tetrahydrofuran medium

Present paper describes the conductivity studies of succinic acid with aqueous PC and THF medium. Limiting molar conductivities and dissociation constant (Kc) were calculated by Kraus-Bray conductivity equations from 288K to 318K. Thermodynamic parameters ∆H, ∆G, ∆S, ∆Es were calculated. keywords: Succinic acid, Conductivity, Pyruvate carboxylase, Tetrahydrofuran. INTRODUCTION In continuation our earlier studies1-3 we focused in the present studies that how succinic acid solvated in water + PC and water + THF medium. Researchers interested in different weak acids in different solvent medium. Study of conductance behaviour of aqueous and non-aqueous medium is much interest in recent past4-6. As succinic acid is weak electrolyte, to determine limiting molar conductance was not measured by Onsagar equation. To determine limiting molar conductance we use Karus-Bray conductivity equation. Many researchers studied the effect of different salts and weak acids in different solvent systems7-15. Our main objective to study to evaluate limiting molar conductance using Karus-Bray equation and also evaluate thermodynamic parameters for supporting the ion-solvation interaction system with this weak acid.


INTRODUCTION
In continuation our earlier studies 1-3 we focused in the present studies that how succinic acid solvated in water + PC and water + THF medium. Researchers interested in different weak acids in different solvent medium.
Study of conductance behaviour of aqueous and non-aqueous medium is much interest in recent past [4][5][6] .
As succinic acid is weak electrolyte, to determine limiting molar conductance was not measured by Onsagar equation. To determine limiting molar conductance we use Karus-Bray conductivity equation.
Our main objective to study to evaluate limiting molar conductance using Karus-Bray equation and also evaluate thermodynamic parameters for supporting the ion-solvation interaction system with this weak acid.

Conductivity study
Conductivity of the above solutions were measured with a conductivity bridge (EC-TDS analyser, CM-183, Elico). Cell constant varied from 1.0+10% to 1.0-10% cm inverse. A temperature control bath (made by PDIC) was used to obtain the conductivities at the higher temperature.

RESULT AND DISCUSSION
Molar conductance data was observed in different composition of succinic acid solution with (water + PC) and (water + THF). As succinic acid is weak electrolyte, to determine limiting molar conductance was not measured by Onsagar equation. To determine limiting molar conductance we use Karus-Bray conductivity equation.
If we plot 1/lm vs. lmC, we get l m 0 value from the intercept and from the slope, we can calculate Kc(dissociation constant).          Table 7 & 8 it has been found that at the same temperature, Ka value increases with increase in solvent proportions, but to some extent different in 40% to 60% in both (water + PC) and (water + THF) systems. As temperature increases, Ka value decreases normally. But some sort of discrepancies observed due to the switchover of ion-pair to ion-solvation interaction or vice versa.
According to the Fuoss, the slope of the plot loglm vs logC is around -0.5, it is an indication of the presence of ion pairs in equilibrium.
From Table 2, succinic acid with (water + PC), the slope was found to be > -0.5. So, it suggests that there was an ion-pair present in equilibrium. Table 3, succinic acid with (water + THF), the slope value was also found. -0.5. So here also observe ion-pair in equilibrium according to Fouss.

From the
From Table 4, for both succinic acid with (water + PC) and (water + THF), as temperature increases, limiting molar conductance value increases. As the viscosity of THF is much lower than PC, so l m 0 value increases with temperature. For this ion-solvent interaction process, activation of salvation is much important. The relation between limiting conductance value and activation solvation energy is related by this equation lm0 = A. e-∆Es/RT (ii) Where A = pre exponential factor, ∆Es = activation salvation energy, R = Molar Gas constant, T= Temperature in K.
If we plot logl m 0 vs 1/T, we get the slope. From the slope value we can easily calculate the activation salvation energy.
From the Table 5 and Table 6, show the value of ∆Es for succinic acid with (water + PC) and (water + THF) in different proportions. ∆Es = 10.54 Kcals for succinic acid with (water + PC)< ∆Es = 12.57 Kcals succinic acid with (water + THF). It indicate that the lower value of activation energy, higher the dissociation as well as higher possibility of ion-solvent interaction than ion-pair interaction.
From these two tables if we compare the dissociation constant value at different temperature for (water + PC) and (water + THF) medium, as temperature increases, Kc value increases. It is more increases for (water + PC) medium as dielectric constant is much more higher than THF medium.
The Gibbs energies of dissociation were calculated using the following equation
The enthalpy change (∆H) of this dissociation process was calculated from the plot logKc vs 1/T. From the slope we can easily evaluate the value of ∆H. From the value of ∆G and ∆H, we can easily calculate ∆S for these systems by the equation Where ∆S = Entropy of solvation Conductance value decreases with increase the percentage of PC as well as THF in water medium. This basic concept supports our result in our present experiment. Thermodynamic parameters were calculated with the help of Kc. ∆H value is negative for both the salvation processes. So it tells that in this dissociation process is exothermic in nature.
∆G value is much higher for (water + PC) medium which an indication of much spontaneous than (water + THF) medium.
∆S value is much negative for (water + PC) medium which indicate that this process is not much disorder for this ion solvent interaction process. At lower temperature, ∆S value is lower negative value. So, at lower temperature, ion solvent interaction is much random.   . shows loglm at infinite dilution with 1/T of succinic acid with (water + THF). From this graph we can evaluate the activation salvation energy with the help of slope. Fig.10. shows the Plot of logKc with 1/T of succinic acid with (water + THF). From the slope we can calculate the ∆H for this system. From this graph we can evaluate the activation salvation energy with the help of slope. Fig. 12. shows the Plot of logKc with 1/T of succinic acid with (water + PC). From the slope we can calculate the ∆H for this system. Figure 13. to Fig. 16 show the Plot of loglm vs logC of succinic acid with (water + PC) at 288K to 318K. From these plots we evaluate the slope. From the slope value we imagine that at equilibrium the systems are ion-pair interaction occurs or not. Figure 13. to Fig.16 show the Plot of loglm vs logC of succinic acid with (water + THF) at 288K to 318K. From these plots we evaluate the slope. From the slope value we imagine that at equilibrium the systems are ion-pair interaction occurs or not.
From these 8 plots it has been found that both systems show ion-pair interaction in equilibrium processes according to Fuoss.
For the further studies in this way we can easily calculate the thermodynamic parameters in different solutions in different concentrations (where different types of interaction happened). So, solution chemistry reveals of different ideas in physical chemistry.

CONCLUSION
From the solavation study of succinic acid with (water + PC) and (water + THF) medium it has been found that with increase in temperature limiting molar conductace increases in both the systems. Degree of dissociation (Kc) increases in both PC and THF medium. But it has been noted that to some extent high for PC medium. This is due to the high dielectric constant value of this medium. In both cases ∆H value is negative. So, these ion-solvent interaction systems are exothermic in nature. ∆G value is much higher for (water + PC) medium which an indication of much spontaneous than (water + THF) medium. ∆S value is much negative for (water + PC) medium which indicate that this process is not much disorder for this ion solvent interaction process. ∆Es = 10.54 Kcals for succinic acid with (water + PC)< ∆Es = 12.57 Kcals succinic acid with (water + THF). It indicate that the lower value of activation energy, higher the dissociation as well as higher possibility of ion-solvent interaction than ion-pair interaction.