3. Results and Discussion
3.1 Excess molar volume
The experimental values of densities for pure components and their binary mixtures as a function of mole fraction at T = (303.15 to 313.15) K are given in Table 2. Excess molar volumes V^E were calculated from the measured values of density using the following equation:
〖 V〗^E = V_m-V_1 x_1-V_2 x_2 (1)
V^E=((x_1 M_1+x_2 M_2)/ρ_m )-((x_1 M_1)/ρ_1 )-((x_2 M_2)/ρ_2 ) (2)
Where, the quantity Vm, V1, V2 relates to the molar volumes of mixture, component 1 and component 2, respectively. x1, x2 & M1, M2 are mole fraction and molar masses of component
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The actual volume change would, therefore, depend on the relative strength of any one of these three interaction effects. The above described factor (II), the effect of interstitial accommodation of one component into the other cannot be possible because molar size of two components are close. The hydrogen bonding seems to play the principal role for making negative value of V^E in present binaries. The effect of interaction between N-formylmorpholine and halobenzenes becomes less intense as electronegativity of halogen group decreases from fluorobenzene to bromobenzene. Negative V^E values observed are in following order: fluorobenzene > chlorobenzene > …show more content…
A perusal of Table 2 and Fig. 2 shows that the values of η are negative over the whole composition range for N-formylmorpholine + fluorobenzene, + chlorobenzene, + bromobenzene mixtures at all three temperatures.
In general, large negative values of η for a binary mixture, accounts for dispersive forces. But in the present study large negative values of η for all selected binaries are expected because there is a large difference in viscosities of pure components. These values suggest the presence of relatively strong interactions which may be a type of Hydrogen bonding or donor- acceptor type of interactions between N-formylmorpholine with halobenzenes [6, 7]. Negative deviations in may occur due to the strong interaction between electronegative halogen group and partially positively charged hydrogen atom of aldehyde (-CHO) group. The values become less negative, as temperature increases from 303.15 to 313.15 K. Fluidity increases in pure components and in mixtures with rise of temperature.
The excess Gibbs energy of activation for viscous flow (∆G^(*E)) for the binary liquid mixture was calculated using following