Search results
Results from the WOW.Com Content Network
In thermodynamics, an activity coefficient is a factor used to account for deviation of a mixture of chemical substances from ideal behaviour. [1] In an ideal mixture, the microscopic interactions between each pair of chemical species are the same (or macroscopically equivalent, the enthalpy change of solution and volume variation in mixing is zero) and, as a result, properties of the mixtures ...
The relative activity of a species i, denoted a i, is defined [4] [5] as: = where μ i is the (molar) chemical potential of the species i under the conditions of interest, μ o i is the (molar) chemical potential of that species under some defined set of standard conditions, R is the gas constant, T is the thermodynamic temperature and e is the exponential constant.
An ideal solution or ideal mixture is a solution that exhibits thermodynamic properties analogous to those of a mixture of ideal gases. [1] [2] The enthalpy of mixing is zero [3] as is the volume change on mixing. [2]
The most significant aspect of this result is the prediction that the mean activity coefficient is a function of ionic strength rather than the electrolyte concentration. For very low values of the ionic strength the value of the denominator in the expression above becomes nearly equal to one.
The non-random two-liquid model [1] (abbreviated NRTL model) is an activity coefficient model introduced by Renon and Prausnitz in 1968 that correlates the activity coefficients of a compound with its mole fractions in the liquid phase concerned. It is frequently applied in the field of chemical engineering to calculate phase equilibria.
The fugacity coefficient is 97.03 atm / 100 atm = 0.9703. The contribution of nonideality to the molar Gibbs energy of a real gas is equal to RT ln φ. For nitrogen at 100 atm, G m = G m,id + RT ln 0.9703, which is less than the ideal value G m,id because of intermolecular attractive forces. Finally, the activity is just 97.03 without ...
The Hildebrand solubility parameter is the square root of the cohesive energy density: δ = Δ H v − R T V m . {\displaystyle \delta ={\sqrt {\frac {\Delta H_{v}-RT}{V_{m}}}}.} The cohesive energy density is the amount of energy needed to completely remove a unit volume of molecules from their neighbours to infinite separation (an ideal gas ).
He also noted that generally the attractive strength between the surface and the first layer of adsorbed substance is much greater than the strength between the first and second layer. However, there are instances where the subsequent layers may condense given the right combination of temperature and pressure.