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The term sublimation refers specifically to a physical change of state and is not used to describe the transformation of a solid to a gas in a chemical reaction. For example, the dissociation on heating of solid ammonium chloride into hydrogen chloride and ammonia is not sublimation but a chemical reaction.
In thermodynamics, the enthalpy of sublimation, or heat of sublimation, is the heat required to sublimate (change from solid to gas) one mole of a substance at a given combination of temperature and pressure, usually standard temperature and pressure (STP). It is equal to the cohesive energy of the solid.
A monotectic reaction consists of change from a liquid and to a combination of a solid and a second liquid, where the two liquids display a miscibility gap. [ 1 ] Separation into multiple phases can occur via spinodal decomposition , in which a single phase is cooled and separates into two different compositions.
The phase diagram shows, in pressure–temperature space, the lines of equilibrium or phase boundaries between the three phases of solid, liquid, and gas. The curves on the phase diagram show the points where the free energy (and other derived properties) becomes non-analytic: their derivatives with respect to the coordinates (temperature and ...
Conditions are so chosen that the solid volatilizes and condenses as a purified compound on a cooled surface, leaving the non-volatile residual impurities or solid products behind. The form of the cooled surface often is a so-called cold finger which for very low-temperature sublimation may actually be cryogenically cooled.
This is an accepted version of this page This is the latest accepted revision, reviewed on 10 December 2024. This article is about the chemical element. For other uses, see Iodine (disambiguation). Chemical element with atomic number 53 (I) Iodine, 53 I Iodine Pronunciation / ˈ aɪ ə d aɪ n, - d ɪ n, - d iː n / (EYE -ə-dyne, -din, -deen) Appearance lustrous metallic gray solid ...
Schematic diagram of the CVT process. Point A is the reaction between the starting materials and the transport agent to form volatile intermediates. These intermediates then are free to move around the inside of the tube via diffusion or convection (point B), and when they reach point C some of the gaseous species react to form solid products.
In its gas phase, RbCl is diatomic with a bond length estimated at 2.7868 Å. [1] This distance increases to 3.285 Å for cubic RbCl, reflecting the higher coordination number of the ions in the solid phase. [2] Depending on conditions, solid RbCl exists in one of three arrangements or polymorphs as determined with holographic imaging: [3]