Apparent molal heat content

Similarly the temperature dependencies of the relative apparent molal heat content can be determined from the heat capacity by ... 

In this book, the values for the heats of formation of substances in aqueous or other solution represent values of the apparent molal heat content, not the partial molal heat content (see Lewis and Randall5 and Rossini5). That is to say, for example, the value of Qf for NaCl (200) means actually the heat of the reaction, Na (c) (g) +200 H20... 

In the case of non-electrolytes, such as urea, mannitol, sucrose, glycine and other amino-acids (ampholytes), and morpholine, the apparent molal heat content is a linear function of the molality m and not of or is a more complicated function, quadratic or cubic, of m. 

In order to relate L2 to the enthalpy of dilution, one must resort to the relative apparent molal heat content... 

Snipes et al. measured the heats of dilution of KCl over a concentration range of. 005 to 2 molal for temperatures from 40 to 80°C. They used the data to fit the relative apparent molal heat content to a polynomial equation calculated the relative partial molal heat contents of the solvent and solute from the relative apparent molsil heat content data. They then fit the partial molal heat contents of the solute to a polynomial equation of the form ... 

Hie molal heats of vaporization of ethanol and acetic acid are 9225 and 5663 cal/g mol. A mixture with ethanol content of Xf = 0.50 is to be separated into products with Xg =0.05 and x -0.95. Pressure is 1 atm, feed is hquid at the boihng point, and tiie reflux ratio is to be 1.3 times the minimum. The calculation of tray requirements is to be made with the true molecular weight 60.05, of acetic acid and witB adjustment to make the apparent molal heat of vaporization the same as that of ethanol, which becomes... 

The relative apparent molar heat contents of sulfuric acid (solute) in mixtures with water (solvent), for various compositions at 25° C, are recorded in Table XXXVl. It may be noted that when L is positive, is negative, and the dilution process is accompanied by the evolution of heat. It is seert, therefore, from Table XXXVI that heat is evolved upon the infinite dilution of sulfuric acid solutions at all concentrations down to the lowest studied, viz., 0.00108 molal. 

The apparent relative molar heat contents of potassium chloride in aqueous solution at 25 C at various molalities are as follows ... 

Fig. 3. Relative apparent heat content vs molality for 1,1,3,3-tetramethyl urea at 30° and 45 °C.

Enthalpy, Entropy, and Heat Capacity of Protein—Water Systems Below 0°C. A number of investigators have reported the apparent enthalpy of fusion as a function of temperature and composition for several hydrated proteins. MacKenzie and coworkers (10) determined absorption isotherms at low temperatures and found that 1) these absorption isotherms have essentially the same sigmoidal shapes as those observed above zero degrees 2) the magnitudes of the values for partial molal enthalpy and entropy increase as the content of unfrozen water decreases 3) the heat of fusion decreases as the content of unfrozen water decreases and 4) the heat capacity of the system increases as the content of unfrozen water increases. Taking these findings all together, the thermodynamic properties of unfrozen water are not very different from those of supercooled water at comparable temperatures. 

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