Specific heat experimental determination

The properties of the hydrogen molecule and molecule-ion which are the most accurately determined and which have also been the subject of theoretical investigation are ionization potentials, heats of dissociation, frequencies of nuclear oscillation, and moments of inertia. The experimental values of all of these quantities are usually obtained from spectroscopic data substantiation is in some cases provided by other experiments, such as thermochemical measurements, specific heats, etc. A review of the experimental values and comparison with some theoretical... 

Thermodynamic data (enthalpy of reaction, specific heat, thermal conductivity) for simple systems can frequently be found in date bases. Such data can also be determined by physical property estimation procedures and experimental methods. The latter is the only choice for complex multicomponent systems. 

Calorimetry experimental technique used to determine the specific heat capacity of a substance or various heats of chemical reactions... 

Specific heats and densities may be assumed to be weight averages if the solids are truly inert otherwise experimental determinations are necessary. The experimental work poses no unusual difficulties in this case. 

There is a simple way by which you can find the approximate atomic weight of an element It is described on pp 211-212 With this method, you determine the specific heat ofthe element experimentally, then divide it into 6 2 (using the rule of Dulong and Petit), the result IS the approximate atomic weight. Even if you didn t know the name of the element, you could use this approximate value along With an accurate chemical analysis to find an act unite value ofthe atomic weight... 

It is relatively easy to determine the solubility parameter of a solvent. The molar volume can be obtained from pycnometry, or a value can possibly be found in the literature. Also, since most solvents of interest have significant volatility, their heats of vaporization can be determined calorimetrically. The experimentally determined heat of vaporization can be converted into the desired energy of vaporization through a conversion term that is simply the change in pressure-volume product for the process. Specifically, AH = AE + A(pV). At constant pressure this is pAV and, to the adequate approximation that the vapor is an ideal gas, the conversion term is thus simply RT (where R is the usual gas constant). 

All the terms in the above equation are either known or can be determined experimentally, except for the value Sm, the specific heat of the metal. The unknown can then be calculated. 

The specific heat of iron is 0.11 cal/g °C thus, from the value of Sm determined experimentally, the unknown metal is iron. 

The experimentally measured specific heat of metal group III nitrides and the phonon determined specific heat for several chosen Debye temperatures are presented in FIGURE 1. 

Equation (6.4) is the general one for vapor pressure, and it shows that the undetermined constant in In P, in Eq. (5.9), is just the chemical constant that we have already determined in Eq. (3.16) of Chap. VIII. The simplest experimental method of finding the chemical constants is based on Eq. (6.4) one measures the vapor pressure as a function of the temperature, finds the specific heats of solid and gas, so that one can calculate the term in the specific heats, and computes the quantity... 

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