Relative partial molar heat content

If the relative partial molar heat content Iri of the solvent (i.e., the differential heat of dilution) is small, as it is for dilute solutions, the activity coefficient of the... 

The relative partial molar heat contents (Li) in cal. mole and the relative, partial molar heat capacities ( pi — Cpi) in cal. deg. mole, of the water in hydrochloric acid solutions are as follows ... 

IR. Relative Partial Molar Heat Contents.—The partial molar thermal properties, namely, heat content and heat capacity, are of particular interest, as well as of practical importance, as will be seen from some of the examples to be given below. In accordance with the general definition ( 26a), the partial molar heat content of any constituent of a solution is represented by... 

For the solvent, the standard state and the reference state are identical, on the basis of the usual convention, and consequently the molar heat content in the reference state may be represented by The partial molar heat content of the solvent in a solution relative to the heat content in the reference state is then 5"i — /u this quantity is called the relative partial molar heat content of the solvent, and is represented by the symbol ii, so that in any solution... 

For the solute, the reference state is the infinitely dilute solution, and although this is not the same as the standard state, the partial molar heat contents are the same in both cases ( 37d). The reference value, which is the partial molar heat content of the solute at infinite dilution, can then be represented by the symbol The relative partial molar heat content L2 in any solution is thus given by... 

Tbe relative partial molar heat contents Li and Lt are also included in the table they are derived from the values, as explained in 44f. 

By determining the mean ionic activity coefficient at several temperatures, e.g., from the elevation of boiling point at different pressures, the values of L% at various concentrations may be calculated from the plot of In (or log 7 ) against either T or 1/T. The relative partial molar heat contents of a few salts have been determined in this manner. ... 

The reverse of this procedure provides one of the main applications of the relative partial molar heat contents. If these are determined by means of thermal measurements, as described in 44f, they can be emoloyed to evaluate the activity coefficients at one temperature if those at another temperature are known ( 38c, 39c). 

By means of equation (44.35), it is evidently possible to determine the relative partial molar heat content of an electrolyte by measuring the E.M.r. of a cell of the type mentioned above at several temperatures, so that the temperature coefficient can be evaluated. This gives the first term on the right-hand side of equation (44.35), and the second term is obtained from the actual e.m.f. s. ... 

The relative partial molar heat content of the solute can thus be determined at any temperature within the range in which equations (44.36) and (44.37) are applicable. 

The relative partial molar heat contents of the constituents of a liquid metallic alloy can be obtained in ati analogous manner by making use of cells of the type described in 38e, viz., Metal A (liquid) Fused salt of A Solution of A in metal B(liquid). In this case the standard state is taken as pure liquid A, and, consequently, , the standard e.m.f., is zero equation (44.34) then becomes... 

If equation (44.2) for the relative partial molar heat content, i.e.,... 

Show that if the vapor behaves as an ideal gas, the relative partial molar heat content Li of the solvent in a solution is given by... 

At finite concentrations the molar enthalpy of hydration of an electrolyte may be estimated by adding the relative partial molar heat content of the solute, Le, to the sum of the cation and anion values of Ahydr fi. The value of Le is numerically equal to and of opposite sign to the experimentally measurable (Harned and Owen 1958 Robinson and Stokes 1965) enthalpy of dilution of the electrolyte, AduHR. At finite concentrations the heat content and the enthalpy of hydration may therefore be smaller or larger than at infinite dilution, depending on the enthalpies involved in the interactions between neighboring ions. 

At finite concentrations of electrolytes, their molar enthalpies of hydration may be estimated by adding the relative partial molar heat content of the solute, L, to the sum of the stoichiometrically weighted cation and anion values of A,yj7/ . The value... 

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