THE FREE ENERGY OF FORMATION OF ZINC OXIDE¹

Abstract

The influence of water on the halogen-hydrogen combinations is discussed. Reasons are advanced for the hypothesis that the primary chemical reaction takes place between halogen atoms and hydrogen. Halogen molecules excited either by light in the visible portion of the spectrum or by thermal collision do not dissociate into atoms except on collision with water molecules. While dissociation does not affect the thermal decomposition of hydrogen iodide, the thermal and photochemical union of hydrogen and bromine and the thermal combination of hydrogen with iodine can be stopped by desiccation.In the combination of hydrogen and bromine the commencement of the chain mechanism, so marked in the hydrogen-chlorine reaction, can be detected a t high temperatures and high pressures of hydrogen. The relationship between the mean life of the excited bromine molecule and the water-vapor pressure required for the attainment of a velocity maximum of combination is developed.sec., this pressure is found to be of the order of 0.1 mm. A mechanism for the combination of hydrogen with iodine based upon the primary dissociation of iodine into atoms is advanced and this system is shown to be photochemically sensitive a t high temperatures (450') in accordance with theoretical considerations. I t is considered unnecessary to assume that the chain mechanism involves water.With a value of 7 = CAMBRIDGE, ENGLANDThis article is the last of three dealing with the free energy of formation of zinc oxide. Four possible methods of experimentally determining the standard free energy of stable oxides usually are available: (1) measurement of high-temperature equilibria and extrapolation of the results; ( 2 ) measurements dependent on the electromotive force of reversible galvanic cells ; (3) calculation from low-temperature specific-heat data and the third law of thermodynamics; (4) calculation from solubility values and standard electrode potentials. The present work reports new experimental resultsPublished by permission of the Director, United States Bureau of Mines.

The Effect of Strength of Bases and Temperature on the Synthesis of Zn‐Al Layered Double Hydroxides by a Non‐Aqueous ‘Soft Chemical’ Sol‐Gel Method and Formation of High Surface Area Mesoporous ZnAl2O4 Spinel

“…Similarly, Zn−Al‐LDH phase was formed only in presence of NaOH and piperidine at 0 o C with hkl reflections of (003), (006), (009) and (012). As the temperature increased Zn(acac) 2 component helped in the formation of only ZnO (Zincite) phases due to the unstability of Zn(OH) 2 at high temperature ,. Thus, it is now further observed not only the temperature, the strength of bases also effect on the synthesis of Zn−Al‐LDH.…”

“…Especially, these factors are important for materials meant for catalytic applications. This method forms particles in the colloidal dispersible size which can be easily coated in the form of crack free thin films over solid inorganic surfaces to prepare catalytic device or separation barrier. Being dispersed in organic media they have other advantage for device fabrication in its material processing step as specialised drying techniques such as supercritical or hypercritical drying could be better utilized easily on organic media than in the aqueous media.…”

“…Being dispersed in organic media they have other advantage for device fabrication in its material processing step as specialised drying techniques such as supercritical or hypercritical drying could be better utilized easily on organic media than in the aqueous media. Report is there about the difficulty faced in the synthesis of Zn−Al‐LDH at room temperature due to the temperature sensitivity of Zinc hydroxide (Zn(OH) 2 ) ,. The synthesis of Zn−Al‐LDH by sol‐gel method using metal acetylacetonate as precursors and the effect of temperature as well as the effect of strength of a series organic bases has not been reported.…”

Fast synthesis of Cu-doped ZnO nanosheets at ambient condition

“…The free energy difference ΔG 0 for reaction at room temperature from Zn(OH) 2 to ZnO is small, −1130 J . Therefore, the co‐existence of Zn(OH) 2 and ZnO in pure water at room temperature is observed .…”

The calorimetry of combustions and related reactions: inorganic reactions

“…The design of microcalorimeters is an active field as 'is attested by the fact that two papers have been contributed to the Symposium on this subject. 2, Since apprec iable amounts of berkelium 14 and californium are expected to be available in a few years,15 it does not seem impossible that combustion measurements will be made on them eventually.…”