Thermodynamic Study of Gaseous Cu₂Sn and CuSn₂ by Knudsen Cell Mass Spectrometry
Abstract
The equilibria involving gaseous species above the condensed Cu-Sn system have been experimentally investigated at elevated temperatures by the high temperature mass spectrometric technique. The molecules Cu₂, CuSn, Sn₂, Cu₂Sn, CuSn₂, and Sn₃ were found to exist in the vapor phase above the liquid Cu-Sn alloy which is predominantly atomic in composition. Third-law enthalpy changes have been determined from the experimental data for the following gaseous reactions: Cu₂ = 2Cu, Sn₂ = 2Sn, Sn₃ = 3Sn, CuSn = Cu + Sn, Cu₂Sn = 2Cu + Sn, Cu₂Sn = Cu₂ + Sn, Cu₂Sn = Sn + 2CuSn, CuSn₂ = Cu + 2Sn, CuSn₂ = Cu₂+ Sn , CuSn₂ + Cu = 2CuSn. The values of the reaction enthalpies have been combined to give the bond dissociation energies, D_o^o, of the diatomic molecules, and the atomization energies, ΔH_(ATM,o), of the various triatomic molecules assuming different molecular structures for the latter.
The previously known molecules Cu₂, Sn₂, Sn₃, and CuSn, have been evaluated, yielding atomization energies of 48.1 ± 2.0, 44.2 ± 1.0, 103.2 ± 0.4, and 39.8 ± 2.0 kcal mole⁻¹ respectively. These values agree within the quoted error limits with the reported literature values. The atomization energies, ΔH_(ATM,o), (in kcal mole⁻¹) are presented for the previously unreported molecules: Cu₂Sn (linear symmetric, 107.9 ± 5.3; bent symmetric, 103.6 ± 5.2; linear asymmetric, 106.7 ± 5.3; bent asymmetric, 102.7± 5.2) and CuSn₂ (linear symmetric, 95.8 ± 2.6; bent symmetric, 95.3 ± 2.6; linear asymmetric, 97.4 ± 2.6; bent asymmetric, 87.9 ± 2.6). The values of the heats of atomization for Cu₂Sn and CuSn₂ were averaged to be 106.0 ± 2.5 and 93.8 ± 4.2 kcal mole⁻¹, respectively. The heats of formation, ΔH°_(f,o), of Cu₂Sn and CuSn₂ were 127.0 ± 2.5 and 130.7 ± 4.2 kcal mole⁻¹, respectively.
Description
Program year: 1977-1978Digitized from print original stored in HDR
Subject
gaseous polyatomic intermetallic moleculescopper
tin
enthalpy
atomization energy
heat of formation
cluster theory testing
Citation
Dufner, Douglas Carl (1978). Thermodynamic Study of Gaseous Cu₂Sn and CuSn₂ by Knudsen Cell Mass Spectrometry. University Undergraduate Fellows. Available electronically from https : / /hdl .handle .net /1969 .1 /CAPSTONE -DufnerD _1978.