The vapor pressure, infrared spectrum, and thermodynamic properties of ZrF4(g)

✍ Scribed by R.J.M. Konings; D.L. Hildenbrand

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 240 KB
• Volume: 26
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.1994.1033

✦ Synopsis

The vibrational spectrum of (\mathrm{ZrF}{4}) in the gas phase was measured by high-temperature infrared spectroscopy. The spectrum showed two strong bands which were assigned to the asymmetric stretching wavenumber (\tilde{v}{3}) and the asymmetric bending wavenumber (\tilde{y}{4}). From a correlation of the established i.r.-inactive wavenumbers in other (\mathrm{MX}{4}) molecules with the i.r.-active values, the two i.r.-inactive modes in (\mathrm{ZrF}{4}) were estimated with an expected accuracy of about (\pm 15 \mathrm{~cm}^{-1}), In addition, the vapor pressure of (\mathrm{ZrF}{4}) (c) was measured in the range (700 \mathrm{~K}) to (850 \mathrm{~K}) by the torsion-effusion technique, yielding for the equilibrium pressure (p_{\mathrm{e}}) :

[
\lg \left(p_{\mathrm{e}} / p^{\circ}\right)=-(11974 \pm 26)(T / K)^{-2}+(10.284 \pm 0.062)
]

where (p^{\circ}=101.325 \mathrm{kPa}). The entropy of (\mathrm{ZrF}{4}(\mathrm{~g})), derived from the second-law entropy of vaporization and the known entropy of the solid, is in close accord with the corresponding statistical value calculated from the vibrational wavenumbers and the reported structural parameters for tetrahedral (\mathrm{ZrF}{4}), showing that the results are internally consistent. Enthalpies of sublimation and thermodynamic properties of (\mathrm{ZrF}_{4}(\mathrm{~g})) are reported.