Search results
Results from the WOW.Com Content Network
Dark green crystals of nickelocene, sublimed and freshly deposited on a cold finger Sublimation of iodine. Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state. [1] The verb form of sublimation is sublime, or less preferably, sublimate. [2]
Camphor (/ ˈ k æ m f ər /) is a waxy, colorless solid with a strong aroma. [5] It is classified as a terpenoid and a cyclic ketone.It is found in the wood of the camphor laurel (Cinnamomum camphora), a large evergreen tree found in East Asia; and in the kapur tree (Dryobalanops sp.), a tall timber tree from South East Asia.
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 sublimatory [1] [2] or sublimation apparatus is equipment, commonly laboratory glassware, for purification of compounds by selective sublimation. In principle, the operation resembles purification by distillation , except that the products do not pass through a liquid phase .
The enthalpy of atomization of an elemental solid is exactly the same as the enthalpy of sublimation for any elemental solid that becomes a monatomic gas upon evaporation. When a diatomic element is converted to gaseous atoms, only half a mole of molecules will be needed, as the standard enthalpy change is based purely on the production of one ...
One exception is phosphorus, for which the most stable form at 1 bar is black phosphorus, but white phosphorus is chosen as the standard reference state for zero enthalpy of formation. [2] For example, the standard enthalpy of formation of carbon dioxide is the enthalpy of the following reaction under the above conditions:
Menthol and camphor, both solids at room temperature, form a eutectic that is a liquid at room temperature in the following proportions: 8:2, 7:3, 6:4, and 5:5. Both substances are common ingredients in pharmacy extemporaneous preparations.
Hess's law states that the change of enthalpy in a chemical reaction is the same regardless of whether the reaction takes place in one step or several steps, provided the initial and final states of the reactants and products are the same. Enthalpy is an extensive property, meaning that its value is proportional to the system size. [4]