Potassium chloride structure

Pure potassium bromide, KBr, which adopts the sodium chloride structure, has the fraction of empty cation sites due to Schottky defects, ncv/Nc, equal to 9.159xl0-21 at 20°C. (a) Estimate the enthalpy of formation of a Schottky defect, Ahs. (b) Calculate the number of anion vacancies per cubic meter of KBr at 730°C (just below the melting point of KBr). The unit cell of KBr is cubic with edge length a = 0.6600 nm and contains four formula units of KBr. 

Inorganic chemistry is the study of the structure, relationships, and interactions of all the nonliving materials that make up the earth s crust, as well as the waters and the atmosphere. Thus, it includes the study of metals, such as iron, mercury, and lead of gases, such as oxygen, hydrogen, and sulphur dioxide of acids, such as sulphuric and hydrochloric of salts, such as sodium chloride (common salt) and potassium chloride, and so on—all the chemicals, in fact, that are not, or have not been, part of living tissue. 

The quality and yield of carbon black depends on the quality of the feedstock, reactor design, and input variables. The structure is controlled by the addition of alkali metals to the reaction or mixing zones. Usual practice is to use aqueous solutions of alkali metal salts such as potassium chloride or potassium hydroxide sprayed into the combustion chamber or added to the make oil in the oil injector. Alkaline-earth compounds such as calcium acetate that increase the specific surface area are introduced in a similar manner. 

As the carbon black structure may be reduced by the presence of alkali metal ions in the reaction zone [4.11], alkali metal salts, preferably aqueous solutions of potassium hydroxide or potassium chloride, are often added to the make oil in the oil injector. Alternatively, the additives may be sprayed separately into the combustion chamber. In special cases, other additives, e.g., alkaline-earth metal compounds which increase the specific surface area are introduced in a similar manner. 

The sodium chloride structure is adopted by most of the alkali metal halides All of the lithium, sodium, potassium, and rubidium halides plus cesium fluoride It is also found in the oxides of magnesium, calcium, strontium, barium, and cadmium... 

Structural effects will probably affect kinetic properties, and as an example we mention the measurements by Brummer and Hills (15) of the volume of activation for potassium chloride conduction in water... 

Just as there are cation channels, there are also trans-membrane channels involved in the transport of biologically important anions such as Cl-. The crystal structure of the CIC chloride channel from Salmonella typhimurium was reported in 2002.3 Along with the determination of the Streptomyces lividans potassium channel structure, this work won a share of the 2003 Nobel prize in chemistry for Roderick MacKinnon (Howard Hughes Medical Institute, New York, USA). Chloride channels catalyse the flow of chloride across cell membranes and play a significant role in functions such as... 

An examination of the distances of shortest internuclear separation r0 between oppositely charged ions in alkali halide crystals with the sodium chloride structure led long ago to the concept of ionic (crystal) radii. For example, if the r0 values for the sodium and potassium salts of the same anion are inspected, it is found that there is an approximately constant difference, irrespective of the nature of the halide ... 

Although most of the focus on solute effects on macromolecular systems has involved proteins, there is evidence that some of the patterns of solute accumulation reflect the dangers that high salt concentrations pose for the covalent structure of DNA. Using cultured mammalian kidney cells Kiiltz and Chakravarty (2001) showed that hyperosmotic stress could cause double strand breaks (dsb) in DNA. Hyperosmolality due to elevated [NaCl] in the culture medium caused the most dsb. Potassium chloride and mannitol led to less damage and, interestingly, no damage to DNA was found in cells exposed to elevated levels of urea. 

In some cases, if the complex ion is not too far from spherical, the compound may assume a structure similar to the simple ones already described, hut with slight distortion. In calcium carbide, for example, the layout of positive and negative ions is the same as in sodium chloride, but the nonspherical Cl ions are lined up with their axes parallel, distending one dimension of the square units to form rectangles. In potassium nitrate, again similar to the sodium chloride structure, the unit cell has been even further distorted from a perfect cube, all faces becoming rhombuses rather than squares. 

The shortest interionic distance in solid potassium chloride is 3.14 A. If the screening constant, S, for ions with the argon structure is 11.25 e, calculate the ionic radii for K+ and Cl". 

The hues are not covalent bonds (Sec. 5.6), only indications of the positions of the ions. Sodium chloride is the most common compound with this structure, which is therefore called the sodium chloride structure. Potassium chloride also has this structure. 

The structure of sodium chloride, which is the prototype for most of the alkali halides, is best described as a cubic closest packed array of Cl- ions with the Na+ ions in all of the octahedral holes [see Fig. 16.42(b)]. The relative sizes of these ions are such that rua 0.66i ci-> so this solid obeys the guidelines given previously. Note that the CP ions are forced apart by the Na+ ions, which are too large for the octahedral holes in the closest packed array of CP ions. Since the number of octahedral holes is the same as the number of packed spheres, all the octahedral holes must be filled with Na+ ions to achieve the required 1 1 stoichiometry. Most other alkali halides also have the sodium chloride structure. In fact, all the halides of lithium, sodium, potassium, and rubidium have this structure. Cesium fluoride has the sodium chloride structure but because of the large size of Cs+ ions, in this case the Cs ions form a cubic closest packed arrangement with the F ions in all the octahedral holes. On the other hand, cesium chloride, in which the Cs+ and CP ions are almost the same size, has a simple cubic structure of CP ions, with each Cs+ ion in the cubic hole in the center of each cube. The compounds cesium bromide and cesium iodide also have this latter structure. 

Solids in which different kinds of atoms occupy structurally equivalent sites have also defect structures. Thus mixed crystals, say of sodium and potassium chlorides (Fig. 99), are examples of defect lattices of this kind. Lithium titanate, LigTiOg, has a rock-salt structure in which cation sites are... 

Potassium chloride occurs as odorless, colorless crystals or a white crystalline powder, with an unpleasant, saline taste. The crystal lattice is a face-centered cubic structure. 

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