Polyatomic substances

Jarvinen represented the molecular attraction in liquids by the equation K=rrfiklr", where m=mass of molecule, r=distance between molecular centres, and k, n are constants n is approximately 5 (5-5 for mercury). He calculated the effect of temperature on the latent heat. The internal pressure for a monatomic substance is pi=alv i, and for a polyatomic substance is n/[z>2/3( i/3 o-242I i/3)5]. The characteristic equation is p= RTjv)f—pi, where (PT / )/=pc=critical pressure. 

Hofmeister, A. M., and Mao, H.-K., Redefinition of the mode Griineisen parameter for polyatomic substances and thermodynamic implications, PNAS Geophys., 99, 559-564 (2002). 

We emphasize that for these comparisons, the equation-of-state parameters were obtained from and P none of the equations were fit to any data on either isotherm. Considering its simplicity, the mRK equation is a remarkable improvement over the older cubic forms. But it is still only a qualitative guide for the high-pressure liquid reproducing the behavior of both liquid and dense-gas phases of polyatomic substances is too much to expect of any simple, two-parameter equation of state. But for another perspective on this issue, see Gregorowycz et al. [32]. 

Mass, considered a fundamental property of matter (II), is defined as a measure of a body s inertia or resistance to a change in body motion upon application of an external force. Having knowledge of a particle s exact mass and some details about its structure is sufficient to identify an element or polyatomic substance. MS is one of most precise, fast, and reliable methods available to determine the molecular and atomic masses of analytes with high accuracy in a single measurement. 

To some extent, for polyatomic substances the errors associated with our incomplete descriptions of elastic and inelastic energy loss are Internally compensating. At moderate to large collision energies the elastic cross sections have been overestimated, while the inelastic values have been underestimated. 

In the harmonic oscillator-rigid rotor approximation polyatomic molecules obey the same separation of their energy into four independent terms as in Eq. (25.4-5). In this approximation the molecular partition function of a polyatomic substance factors into the same four factors as in Eq. (25.4-6). The translational partition function is given by... 

Since the vibrational energy is a sum of 3n - 5 or 3n - 6 terms and since the quantum numbers for each vibration are independent of each other, the vibrational partition function of a polyatomic substance is a product of factors, and each factor is analogous to that of a diatomic molecule ... 

For a diatomic substance or a polyatomic substance with linear molecules the rotational energy is given by... 

For a polyatomic substance with nonlinear molecules, Zrot is proportional to so that... 

For a polyatomic substance, the vibrational energy contains one term for each normal mode ... 

Zrot,ci = SjT IekBT (diatomic or linear polyatomic substance)... 

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