Slightly soluble solid

One way to establish equilibrium between a slightly soluble solid and its ions in solution is to stir the solid with water to form a saturated solution. As you might expect, the solubility of the solid, s, in moles per liter, is related to the solubility product constant, Ksp. In the case of barium sulfate dissolving in water we have... 

Mass transfer to liquids in turbulent pipe flow has been studied by using tubes made from a slightly soluble solid and measuring the rate of dissolution of the solid for various liquid flow rates. An alternate technique is to make a portion of the tube wall an electrode and carry out an electrochemical reduction under conditions where the current is limited by the rate of mass transfer of the reacting ion to the wall. 

A new batch microcalorimeter has been developed for measuring the dissolution of small amoimts of easily or slightly soluble solids. The calorimeter has been calibrated by dissolution of potassium chloride and successfully tested by measurements of the enthalpies of dissolution of acetanilide and adenine [16]. 

To predict whether a given pair of dissolved ions will form a solid when mixed, we must know some facts about the solubilities of various types of ionic compounds. In this text we will use the term soluble solid to mean a solid that readily dissolves in water the solid "disappears" as the ions are dispersed in the water. The terms insoluble solid and slightly soluble solid are taken to mean the same thing a solid where such a tiny amount dissolves in water that it is undetectable with the naked eye. The solubility information about common solids that is summarized in Table 7.1 is based on observations of the behavior of many compounds. This is factual knowledge that you will need to predict what will happen in chemical reactions where a solid might form. This information is summarized in Figure 7.3. 

This is an example of rapid chemical reaction in the laminar boundary layer on a flat plate. Consider the steady-state dissolution of a slightly soluble solid in a flowing dilute solution, and suppose the solid is acidic whereas the flowing solution is basic [23]. The geometry under consideration is a flat plate consisting of acid, located at zero incidence to the flow. The process may be assumed isothermal, and the fluid properties are to be treated as independent of position. 

A significant amount of research has been performed on the measurement of liquid-solid mass transfer [67], Generally, liquid-solid mass transfer in fixed-bed reactors has been studied by five methods dissolution of slightly soluble solids into the liquid [68-73], chemical reaction with significant liquid-solid mass transfer resistance [74], ion exchange followed by an instantaneous irreversible reaction [75], dynamic absorption [76], and electrochemical technique [77-80]. The electrochemical method has certain advantages over the other it facilitates direct and instantaneous measurements of solid-liquid mass transfer and is thus very useful to measure mass transfer fluctuations, especially under pulse flow conditions. 

Consider the chemical dissolution of a slightly soluble solid reactant A in a liquid with excess reactant B, This type of reaction is encountered frequently in organic syntheses. This situation resembles the solid surface reaction that was treated in section 5,3,2,2, but the difference is that now the solid dissolves first and then reacts in the liquid phase (therefore the solid reactant is now denoted as A). When the reaction is relatively slow (tp < 0.3), eq. (5.21) is to be applied here. For the situation where the rate is completely determined by mass transfer of the slightly soluble A into the solution with a large excess of B, the effective rate constant is now the mass transfer coefficient of A, and the calculations similar to those in section 5,3,2,2 apply here also. The mass balance for n particles per unit volume is then... 

Peroxide. Alkaline or neutral manganese(II) is oxidized to Mn02 aq by HO2. Cold, concentrated KOH, plus Mn and H2O2, give brownish, slightly soluble solids written variously as K4[Mn(02)4] etc. These products explode above 0 C. 

High-temperature dehydration (800 °C) above the melting temperature of NaH2P04 (628 °C) yields a liquid with very high relative molecular mass, which gives slightly soluble solids of formula (NaP03) ... 

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