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Reversible transformation

Umsetzung, /. transposition double decomposition conversion, change transformation reversal reaction transplantation exchange, sale, business. Umsetzungsgeschwindigkeit, /. velocity of transformation, reaction rate. [Pg.463]

The phase relationship between the most commonly known tetragonal phase CaC2-I and phase(s) II (or III) is still in question. CaC2-I transforms reversibly into the cubic phase IV, as does the phase (II -r) III. It is interesting to note that the cubic phase IV seems to have a memory for its respective precursor phase (III or I) that is regained after cooling down phase IV. The synthesis of... [Pg.124]

Despite the asymmetry between the forward and reverse current or charge responses, reversibility may be strictly defined by the transformations depicted in Figure 1.4. The anodic trace is first measured against the prolongation of the forward trace (the trace that would have been obtained if the forward scan had been prolonged beyond the inversion potential), as symbolized by a series of vertical arrows. After symmetry about the horizontal axis, the resulting curve is shifted to the initial potential in the case of the time dependence representation. Alternatively, in the case of the potential dependence representation, another symmetry about E = E° is performed. In both cases, reversibility, in both the chemical and electrochemical senses, is demonstrated by the exact superposition of the hence-transformed reverse trace with the forward trace. [Pg.9]

The formation of water from gaseous hydrogen and oxygen is a spontaneous reaction at room temperature, although its rate may be unobservably small in the absence of a catalyst. At 298.15 K, the heat of the irreversible reaction at constant pressure is — 285,830 J mol . To calculate the entropy change, we must carry out the same transformation reversibly, which can be performed electrochemicaUy with a suitable set of electrodes. Under reversible conditions, the heat of reaction for Equation (6.99) is —48,647 J mol. Hence, for the irreversible or reversible change... [Pg.139]

The method of determination from measurements of cell potentials depends on the possibility of carrying out a transformation reversibly in an electrical cell. (See Fig. 7.2.) In this case, the spontaneous tendency of the transformation wUl be opposed by an opposing potential just sufficient to balance the potential in the electrical ceU produced by that spontaneous tendency. The potential observed under such circumstances is related to the change of the Gibbs function for the reaction by Equation (7.84)... [Pg.284]

To explain the observed kinetics, it has been postulated that, with hydrogen ions as catalyst, normal unreactive H3PO2 is transformed reversibly into an active form, the nature of which is unknown. This intermediate then reacts with the oxidizing agent to give H3PO3. Show that this scheme does explain the observed kinetics. [Pg.37]

Alkenes. Addition of diborane and organoboranes to carbon-carbon double bonds is a rapid, quantitative, and reversible transformation. Reversibility, however, is not a severe limitation under the usual reaction conditions, since thermal dissociation of organoboranes becomes significant only above 100°C. The addition is syn and occurs in an anti-Markovnikov manner that is, boron adds preferentially to the less substituted carbon atom. The attack of the reagent takes place on the less hindered side of the reacting alkene molecule. [Pg.316]

Polymorphs and pseudopolymorphs can also be classified as monotropes or enantiotropes, depending upon whether or not one form can transform reversibly to another. In a monotropic system. Form I does transform to Form II, because the transition temperature cannot appear before the melting temperature (Fig. 5,... [Pg.203]

The most stable allotrope is orthorhombic sulfur (the a-form and standard state of the element) and it occurs naturally as large yellow crystals in volcanic areas. At 367.2 K, the ot-form transforms reversibly into monoclinic sulfur (j3-form). Both the a- and jB-forms contain Sg rings the density of the a-form is 2.07gcm , compared with... [Pg.439]

Obviously, we cannot actually conduct a transformation reversibly. An infinite length of time would be required if the volume increment in each stage were truly infinitesimal. Reversible processes therefore are not real processes, but ideal ones. Real processes are always irreversible. With patience and skill the goal of reversibility can be very closely approached, but not attained. Reversible processes are important because the work effects associated with them represent maximum or minimum values. Thus limits are set on the ability of a specified transformation to produce work in actuality we will get less, but we must not expect to get more. [Pg.113]

F. 13. DSC thermogram of a-TTP (4) heated from 25 25 °C (heating rate 8 °C min ). Temperatures of thermal events are defined as the beginnings of such events. The regions labelled refer to the following thermal reactions I. Phase transformation (reversible) II. Phase transformation... [Pg.125]

A non-crystalline polymer can be transformed reversibly into another form by a temperature change (Fig. 3.5). Alternatively an irreversible crosslinking reaction can convert a linear polymer into a network polymer. This reaction can only occur when polymer chains can change shape, i.e. the polymer is... [Pg.59]

With a very small concentration, for example 1/4000%, only diffuse accumulation occurs in the vacuole (Fig. 42a). The two states a and b of Fig. 42 can further be transformed reversibly into one another by changing the neutral red concentration in the liquid flowing along the membrane. [Pg.474]

All four states a, 6, c and d, can be transformed reversibly into each other by changing the neutral red concentration or the pH. [Pg.475]

An a-form separates from the melt which is transformed reversibly into a sub-a form ( a 8-form) at about 25 °C lower temperature. Alternatively the a-form is transformed irreversibly into a -form. There are furthermore two 8-forms, but they are so closely related in structure (the same bilayer units) that only one form is indicated in the scheme above. The 8 -and j8-forms can also be crystallized from solvents. [Pg.362]

L-Glutamic acid is formed from (%-ketoglutaric acid, an intermediate of the tri-carbonic acid cycle (D 5) by glutamate dehydrogenase. It is transformed reversibly to L-proline and L-ornithine (Fig. 217). [Pg.357]

Severe nutritional deficiencies, X-irradiation, the administration of antifolic (see Fig. 4-48) or bactericidal agents allow some bacteria of the intestinal lumen to pass through the mucosa and enter the bloodstream to cause septicemia. Furthermore, the endotoxins normally present in the intestinal lumen enter the bloodstream under certain pathological conditions and transform reversible shock into irreversible shock. All gram-negative bacteria produce endotoxins—large molecules with a molecular weight of 1,000,000 formed of a complex of proteins, lipids, and polysaccharides. [Pg.323]

Silica, with the chemical formula Si02 and relative molar mass of 60.084, exhibits a complex polymorphism characterized by a large number of reversible and irreversible phase transformations (Figure 10.1) usually associated with important relative volume changes (AV/V). At low temperature and pressure beta-quartz (P-quartz) [14808-60-7] predominates, but above 573°C, it transforms reversibly into the high-temperature alpha-quartz (a-quartz) [14808-60-7] with a small volume change (0.8 to 1.3 vol.%) ... [Pg.594]

On cooling a-cristoballite transforms reversibly into beta-cristoballite (P-cristoballite, cubic) at 260°C with a volume change 0 2.0 to 2.8 vol.% ... [Pg.594]


See other pages where Reversible transformation is mentioned: [Pg.463]    [Pg.118]    [Pg.54]    [Pg.1543]    [Pg.177]    [Pg.248]    [Pg.126]    [Pg.259]    [Pg.503]    [Pg.157]    [Pg.1542]    [Pg.155]    [Pg.259]    [Pg.209]    [Pg.363]    [Pg.385]    [Pg.392]    [Pg.498]    [Pg.195]    [Pg.581]    [Pg.252]    [Pg.168]    [Pg.140]    [Pg.34]    [Pg.787]    [Pg.91]    [Pg.145]    [Pg.1054]   
See also in sourсe #XX -- [ Pg.138 ]




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Reverse transform

Reverse transformation

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