Stoichiometry limiting reactions

Shortly after, we recognized that ScCu4Ga2 (Im3) [70] might also be tuned to a QC, but the correct stoichiometry and reaction conditions were not achieved in our limited experiments. Recently, Honma and Ishimasa [71] have reported that i-QC phase forms almost exclusively from a rapidly quenched ScisCu48Ga34 composition, emphasizing a very narrow phase width and its thermodynamic metastability at room temperature. However, the failure turned us to other Ga intermetallics, which led to the pseudogap tuning concepts that follow. 

Reaction stoichiometry Limiting reactants Percent yield... 

Introduction and Orientation, Matter and Energy, Elements and Atoms, Compounds, The Nomenclature of Compounds, Moles and Molar Masses, Determination of Chemical Formulas, Mixtures and Solutions, Chemical Equations, Aqueous Solutions and Precipitation, Acids and Bases, Redox Reactions, Reaction Stoichiometry, Limiting Reactants... 

VolCal2 Limiting Reactions - Calculation of Stoichiometry Factors - Working Method - Volumetric Calculations. 

Limited reaction times or incomplete byproduct removal can control the conversion in a self-condensing polymerization. How does the PD of these polymers compare to those in Example 13.2 where the reaction went to completion with imperfect stoichiometry Make the comparison at the same average chain length. 

The stoichiometry of Reaction III limits its occurrence to systems in which both steam and hydrogen are present. Although this reaction is the stoichiometric sum of Reactions I and II, this model considers it to be a third, independent gasification reaction. Reaction III, arbitrarily... 

This reaction was used in the small-scale production of chlorine. It operated under modest conditions (100-110°C), but corrosion problems were severe and the stoichiometry limited the recovery of chlorine to 50%. Practical values were 35-40%. On the positive side, the reactor gas had a high ( 90%) concentration of chlorine [6]. In early operation, manganese chloride was a waste product. In 1866, Weldon achieved recycle of the manganese value by treating the chloride with lime while steaming with air or oxygen at 55-60°C ... 

Given the higher rates associated with the fast SCR chemistry, the NO2-feed concentration plays an important role in controlling the DeNO activity at low temperatures. Figure 8 shows typical results for a V-based catalyst, pointing out that for T < 300° C the highest NO conversions are indeed always obtained for equimolar amounts of NO2 and NO, in agreement with the stoichiometry of reaction 3 (15). Notably, the activity enhancement due to NO2 is substantial at 200°C the NO conversion is limited to about 10% in the absence of NO2, but it increases to 70% with a 1 1 NO/NO2 feed mixture. Similar effects of the NO2 feed content have been reported for Fe-promoted zeolites (30). 

Let s return to our pancake analogy to xmderstand two more concepts important in reaction stoichiometry limiting reactant and percent yield. Recall our pancake... 

As was to be expected on the basis of the stoichiometry of reaction 2, the limiting current determined [36] as a function of PcoJPo2 found to have a maximum at PcoJPo2 limiting current of curve b in Fig. 87 is the largest one for this reason. The currents above the limiting current of reaction 2 increase with the oxygen pressure. 

Yamazaki and Souzi (1958, 1960) have been able to produce evidence that the oxidation occurs by a mechanism essentially similar to that obtaining for triose reductone. The limiting reaction is that of lAA with compound II (3 x 10 sec at 13°C.) to form an indoleacetic radical. The subsequent course of the reaction depends on the interactions of that radical with oxygen and other acceptors present it can also produce a reaction with, and inactivation of, the peroxidase itself. They show that the effect of manganese is upon the reaction with oxygen in this as in many other cases and suggest that the OjffAA stoichiometry of 1.0 is to be explained as a consequence of the complexity of the subsequent reactions of the radical, for example ... 

In principle, Chen, given the flux relations there is no difficulty in constructing differencial equations to describe the behavior of a catalyst pellet in steady or unsteady states. In practice, however, this simple procedure is obstructed by the implicit nature of the flux relations, since an explicit solution of usefully compact form is obtainable only for binary mixtures- In steady states this impasse is avoided by using certain, relations between Che flux vectors which are associated with the stoichiometry of Che chemical reaction or reactions taking place in the pellet, and the major part of Chapter 11 is concerned with the derivation, application and limitations of these stoichiometric relations. Fortunately they permit practicable solution procedures to be constructed regardless of the number of substances in the reaction mixture, provided there are only one or two stoichiomeCrically independent chemical reactions. 

Almost any chemical reaction can serve as a titrimetric method provided that three conditions are met. The first condition is that all reactions involving the titrant and analyte must be of known stoichiometry. If this is not the case, then the moles of titrant used in reaching the end point cannot tell us how much analyte is in our sample. Second, the titration reaction must occur rapidly. If we add titrant at a rate that is faster than the reaction s rate, then the end point will exceed the equivalence point by a significant amount. Finally, a suitable method must be available for determining the end point with an acceptable level of accuracy. These are significant limitations and, for this reason, several titration strategies are commonly used. 

As with other problems with stoichiometry, it is the less abundant reactant that limits the product. Accordingly, we define the extent of reaction p to be the fraction of A groups that have reacted at any point. Since A and B groups... 

Nitrogen forms binary compounds with almost all elements of the periodic table and for many elements several stoichiometries are observed, e.g. MnN, Mn Ns, Mn3N2, MniN, Mn4N and Mn tN (9.2 < jc < 25.3). Nitrides are frequently classified into 4 groups salt-like , covalent, diamond-like and metallic (or interstitial ). The remarks on p. 64 concerning the limitations of such classifications are relevant here. The two main methods of preparation are by direct reaction of the metal with Ni or NH3 (often at high temperatures) and the thermal decomposition of metal amides, e.g. ... 

A limiting reactant is that reactant which is present in the smallest stoichiometric amount. In industrial reactions, the reactants are not necessarily supplied in the exact proportions demanded by the stoichiometry of the equation. Under these... 

Examine the stoichiometry of the chemical reaction, and identify the limiting reactant and excess reactants. 

In the schemes considered to this point, even the complex ones, the products form by a limited succession of steps. In these ordinary reaction sequences the overall process is completed when the products appear from the given quantity of reactants in accord with the stoichiometry of the net reaction. The only exception encountered to this point has been the ozone decomposition reaction presented in Chapter 5, which is a chain reaction. In this chapter we shall consider the special characteristics of elementary reactions that occur in a chain sequence. 

The stoichiometry of the redox reactions of conducting polymers (n and m in reactions 1 and 2) is quite variable. Under the most widely used conditions, polypyrroles and polythiophenes can be reversibly oxidized to a level of one hole per ca. 3 monomer units (i.e., a degree of oxidation, n, of ca. 0.3).7 However, this limit is dictated by the stability of the oxidized film under the conditions employed (Section V). With particularly dry and unreactive solvents, degrees of oxidation of 0.5 can be reversibly attained,37 and for poly-(4,4 -dimethoxybithiophene), a value of n = 1 has been reported.38 Although much fewer data are available for n-doping, it appears to involve similar stoichiometries [i.e., m in Eq. (2) is typically ca. 0.3].34,39"41 Polyanilines can in principle be reversibly p-doped to one... 

Fig. 8.9 A typical stoichiometry question on limiting reagents and amount of product formed in a reaction...

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