What Is the Standard Molar Enthalpy of the Formation of Tungsten Diiodide?

The standard molar enthalpy of formation of tungsten diiodide is -8.37 kJ/mol. The standard molar enthalpy of formation of tungsten diiodide, Δ_fH_m^θ(WI₂, g, 298 K), is defined as the standard molar enthalpy of formation for the reaction to produce the substance tungsten diiodide (ν_B=+1) from the monomers of the reference state at 298 K. The standard molar enthalpy of formation is -8.37 kJ/mol.

By comparing the standard molar enthalpy of formation data for certain compounds of the same type, the relative stability of these compounds can be inferred. Determination of the enthalpy of the formation of compounds is long-needed basic research in the field of metallurgy and materials, and this value can be obtained by experimental measurements. There are many methods for determining the thermodynamic standard enthalpy of the formation of compounds, and experimental results for the same compound often vary, and the reliability of the experimental methods has yet to be investigated. In the existing inorganic compounds, the physical properties of most of the phases are unknown or uncertain, and various thermodynamic data manuals and electronic databases are only for the known data, while more thermodynamic data are unavailable, so the physical property estimation methods established by theoretical analysis and experimental laws are very important.

A common method is to use calorimetry, in which a known mass of WI₂ solid is added to a hot vessel at a constant temperature and reacted with a known amount of oxygen, thereby measuring the amount of heat released or absorbed during the reaction (i.e., the heat of reaction). The standard enthalpy of the reaction can then be used to calculate the standard molar enthalpy of the formation of WI₂.

According to thermochemical data, the standard molar enthalpy of the formation of tungsten iodide is -8.37 kJ/mol. This means that, in the standard state, 8.37 kJ of heat energy will be released from the system when 1 mol of WI₂ solid forms 1 mol of WI₂ gas.

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