Dissolution of solids in liquids

The amonnt of energy involved in this process dejrends on the electrostatic attraction between ions in the sohd. When these attractions are strong due to higher charges and/or small ion sizes, a large amount of energy is released as the solid forms, increasing its stability. 

The reverse of the crystal formation reaction is breaking the crystal into separated gas phase ions. 

If the solvent is water, the energy that must be supplied to expand the solvent (Step b in Fignre 14-1) inclndes that required to break up some of the hydrogen bonding between water molecnles. 

Un less otheiwise noted, a II content on this page is Cengage Learning. 

Hydration is usually highly exothermic for ionic or polar covalent compounds hecause the polar water molecules interact very strongly with ions and polar molecules. In fact, the only solutes that are appreciably soluble in water either undergo dissociation or ionization or are able to form hydrogen bonds with water. 

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Batch Stirred Tanks Tanks agitated by coaxial impellers (turbines, paddles, or propellers) are commonly used for batch dissolution of solids in liquids and may be used for leaching fine solids. Insofar as the controlhng rate in the mass transfer is the rate of transfer of mate-... 

Main relationships governing dissolution of solids in liquids... 

Besides fluid mechanics, thermal processes also include mass transfer processes (e.g. absorption or desorption of a gas in a liquid, extraction between two liquid phases, dissolution of solids in liquids) and/or heat transfer processes (energy uptake, cooling, heating, drying). In the case of thermal separation processes, such as distillation, rectification, extraction, and so on, mass transfer between the respective phases is subject to thermodynamic laws (phase equilibria) which are obviously not scale dependent. Therefore, one should not be surprised if there are no scale-up rules for the pure rectification process, unless the hydrodynamics of the mass transfer in plate and packed columns are under consideration. If a separation operation (e.g. drying of hygroscopic materials, electrophoresis, etc.) involves simultaneous mass and heat transfer, both of which are scale-dependent, the scale-up is particularly difficult because these two processes obey different laws. 

Consider a system consisting of a completely miscible solution of solute and solvent in all proportions. One should consider dissolution of solids in liquids as occurring... 

In practice, one mostly encounters problems of corrosion with melts which are related to the dissolution of solids in liquids. However, there are several specific features ... 

The dissolution of solids in liquids arises often in practice because the liquid phase provides a more homogeneous environment for contact between components as well as for chemical reactions. Solids generally have a finite solubility in a liquid solvent. Exceeding the solubility limit produces a two-phase system, a solid in contact with the solution. This problem of solid liquid equilibrium (SLE) is treated by the same general thermodynamics tools developed so far. When the liquid is saturated in the solid component (solute), the solute satisfies the equilibrium criterion. 

Dissolution of Solids in Liquids 14-3 Dissolution of Liquids in Liquids (Miscibility)... 

An expression of this sort was suggested as early as 1897 [45] for the dissolution of solids in liquids. These expressions are, of course, analogous to the definition of a heat-transfer coefficient h q h(t — /j)- Whereas the concept of the heat-transfer coefficient is generally applicable, at least in the absence of mass transfer, the coefficients of Eqs. (3.3) and (3.4) are more restricted. Thus,J ... 

Examples of this type often occur in chemical and metallurgical processes the combustion and gasification of carbon and coal, the decomposition of solids into gases, the dissolution of solids in liquids, formation of metal carbonyls, fluorination and chlorination of metals, and some electrochemical processes. 

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