Browsing by Author "Srivastava, R. D."

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Effusion-Mass Spectrometric Study of Thermodynamic Properties of Vanadium and Vanadium Nitride
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (2), 1973) Farber, Milton; Srivastava, R. D.
Effusion-mass spectrometric studies were performed on the vapour species in equilibrium above VN(c) in the temperature range 1900 to 2412 K. From an analysis of the reactions involved, ΔHf298 values of 122.4 ± 5 kcal/mol (second law) and 120.4 ± 2 kcal/mol (third law) were obtained for VN(g), yielding a dissociation energy, D°298, for gaseous VN of 114.1 kcal/mol. An appearance potential of 8 ± 1 eV was recorded for VN(g). The thermodynamic analysis of the vapour species over the solid state yielded a second law ΔHf of –52 ± 1.5 kcal/mol for VN(c). Studies made in this temperature range resulted in a third law heat of fusion of 4.30 ± 0.45 kcal/mol for vanadium. The second and third law mass spectrometric ΔHf298 values of 122.8 ± 1.5 and 123.0 ± 0.2 kcal/mol, respectively, for V(g) were in good agreement with Knudsen third law weight loss experiments at 2092 and 2122 K, which yielded ΔHf298 values of 123.3 and 122.9 kcal/mol.
Experimental Determination of Heats of Formation of Negative Ions and Electron Affinities of Several Boron and Aluminium Fluorides
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Srivastava, R. D.; Uy, O. M.; Farber, Milton
Thermodynamic properties for the negative ions of boron and aluminium fluorides were obtained by means of the effusion-mass spectrometric method over the temperature range 1100 to 1900 K. Studies were conducted involving negative ions with neutral molecules for the isomolecular reactions BF–2(g)+ F(g)→BF2(g)+ F–(g), BF3(g)+ BF–2(g)→BF(g)+ BF–4(g), AlF2(g)+ F–(g)→AlF–2(g)+ F(g) and 2AlF2(g)+ AlF–2(g)→2AlF(g)+ AlF–4(g). The heats of formation, ΔHf298, for the ions BF–2(g), AlF–2(g), AlF–4(g), and BF–4(g) obtained from the reaction thermodynamics were – 191.7 ± 3, – 232.1 ± 3, – 500 ± 3 and [gt-or-equal]– 433 kcal mol–1, respectively. The electron affinities for BF2 and AlF2 were 50.7 ± 3 and 53.1 ± 3 kcal mol–1, respectively.
Mass spectrometric determination of the heats of formation of the silicon fluorides SiF(g), SiF2(g) and SiF3(g)
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (05), 1978) Farber, Milton; Srivastava, R. D.
An effusion-mass spectrometric study of the reaction of SiF4(g) with Si(c, 1) in the temperature range 1590–1782 K has been completed. Second and third law reaction enthalpies were obtained for SiF4(g)+ Si(g)= 2SiF2(g), SiF4(g)+ SiF2(g)= 2SiF3(g), and SiF2(g)+ Si(g)= 2SiF(g). From the heats of reaction third law ΔHf298 values of –5.8 ± 0.5, –140.6 ± 0.3 and –259.3 ± 0.5 kcal mol–1 were obtained for SiF(g), SiF2(g) and SiF3(g), respectively. For the dissociation of SiF(g)→(3P0)Si(g)+(2P[fraction three-over-two])F(g) a third law dissociation energy value of 131.2 ± 0.5 kcal mol–1 was calculated.
Mass Spectrometric Determination of the Thermodynamic Properties of the Vapour Species from Alumina
(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (2), 1972) Farber, Milton; Srivastava, R. D.; Uy, O. M.
The vapour species over Al2O3(c) were determined mass spectrometrically from an alumina effusion cell. These data are in good agreement with previously published weight loss data since the partial pressures of the suboxides, AlO, Al2O, AlO2 and Al2O2 were found to be of the same order as those of the elements, Al and O. New values were determined for the ΔHf298K of AlO, Al2O, AlO2 and Al2O2 of 17.0 ± 2.0, –33.2 ± 3.0, –44.3 ± 2.0 and –113.6 ± 2.0 kcal/mol, respectively. Excellent agreement was obtained between second and third law studies.