Mass action effect

The extent of displacement depends on the relative stabiUties of the complexes and the mass action effect of an excess of M For equivalent total amounts of M and M, K must be on the order of 10 for 99% complete displacement to occur. Similar considerations apply for the displacement of L from ML by U. The situation is quite analogous to the familiar competition of two bases for the hydrogen ion. 

Titrations can be carried out in cases in which the solubility relations are such that potentiometric or visual indicator methods are unsatisfactory for example, when the reaction product is markedly soluble (precipitation titration) or appreciably hydrolysed (acid-base titration). This is because the readings near the equivalence point have no special significance in amperometric titrations. Readings are recorded in regions where there is excess of titrant, or of reagent, at which points the solubility or hydrolysis is suppressed by the Mass Action effect the point of intersection of these lines gives the equivalence point. 

Although the exact chemical mechanism for the direct oxide reduction reaction has not yet been fully characterized, it has been well established that the reaction goes to completion when excess calcium is present, sufficient CaCl2 is available to dissolve the CaO produced, and adequate stirring is used. As calcium metal is soluble to about 1 wt% in CaC12 at 835°C, excess Ca insures that the reaction is driven to completion by mass-action effects. 

The cation which is both solvated by M and paired Pn+M-A Whichever way one thinks of this species, the positive charge-density of the Pn+M is low compared to that of Pn+ so that for this reason and because of the mass-action effect the abundance of Pn+M A is likely to be much less than those of Pn+A" and Pn+M. 

Polymerisations of undiluted, bulk monomer are rare except for those initiated by ionising radiations and they require a special treatment which will be given later. The most common situation is to have the propagating ions in a mixture of monomer and solvent, and as the solvation by the solvent is ubiquitous and may dominate over that by other components of the reaction mixture, mainly because of the mass-action effect, it will not be noted by any special symbol, except in a few instances. This means that we adopt the convention that the symbol Pn+ denotes a growing cation solvated mainly by the solvent correspondingly kp+ denotes the propagation constant of this species, subject to the proviso at the end of Section 2.3. Its relative abundance depends upon the abundance of the various other species in which the role of the solvent as the primary solvator has been taken over by any or all of the anion or the monomer or the polymer. The extent to which this happens depends on the ionic strength (essentially the concentration of the ions), and the polarity of the solvent, the monomer and the polymer, and their concentrations. 

The concentration of ammonia in the liver is not saturating for carbamoyl phosphate synthetase, so that the greater the flux of ammonia into or within the liver, the higher the concentration of ammonia and the higher the activity of the synthetase. The effect of ammonia concentration is, therefore, a mass-action effect. 

The moduli of model polyurethane networks clearly show reductions below the values expected for perfect networks, with the reductions increasing with pre-gel intramolecular reactlon(5-7). The reductions can be shown to be too large to come solely from pre-gel loop forma-tion( ), some must occur post-gel. In addition, extrapolation to conditions of zero pre-gel intramolecular reaction, by increasing reactant concentrations, molar masses of reactants or chain stiffness, still leaves a residual proportion of inelastic chains due to gel-gel intramolecular reaction. It is basically a law-of-mass-action effect( ). The numbers of reactive groups on gel molecules are unlimited. Intramolecular reaction occurs, and some of this gives Inelastic chains. Only a small amount of such reaction has a marked effect on the modulus. 

The Universal Occurrence of Imperfections (Law-of-Mass-Action Effect)... 

The positive intercepts in Figure 7 show that post-gel(inelastic) loop formation is influenced by the same factors as pre-gel intramolecular reaction but is not determined solely by them. The important conclusion is that imperfections still occur in the limit of infinite reactant molar masses or very stiff chains (vb - ). They are a demonstration of a law-of-mass-action effect. Because they are intercepts in the limit vb - >, spatial correlations between reacting groups are absent and random reaction occurs. Intramolecular reaction occurs post-gel simply because of the unlimited number of groups per molecule in the gel fraction. The present values of p , (0.06 for f=3 and 0.03 for f=4 are derived from modulus measure- ments, assuming two junction points per lost per inelastic loop in f=3 networks and one junction point lost per loop in f=4 networks. 

Extrapolation of pj. g to the limit of zero pre-gel intramolecular reaction for given reaction systems shows that post-gel intramolecular reaction always results in network defects, with significant increases in Mg above Mg. Such post-gel intramolecular reaction is characterised as pg g. The variation of pg g with intramolecular-reaction parameters shows that even in the limit of infinite molar mass, i.e. no spatial correlation between reacting groups, inelastic loops will be formed. The formation may be considered as a law-of-mass-action effect, essentially the random reaction of functional groups. Intramolecular reaction under such conditions (p2 ) must be post-gel and may be treated using classical polymerisation theory. 

When enantiomerically pure (/ )- and (S)-ll were reacted with racemic 1-bromo-l-phenylethane (13), d.r. s of 97 3 were obtained. The somewhat lower d.r. obtained on reaction of the resolved complexes was explained as a mass action effect during the course of the reaction the reactive enantiomer of the haloalkane is depleted relative to the less reactive enantiomer. 

The addition of cobalt hydrocarbonyl to olefins has been investigated and information on the detailed mechanism of the reaction obtained. The reaction of 1-pentene with cobalt hydrocarbonyl to produce a mixture of 1- and 2-pentylcobalt tetracarbonyls was shown to be inhibited by carbon monoxide (46). The inhibition very likely arises because the reactive species is cobalt hydrotricarbonyl rather than the tetracarbonyl. The carbon monoxide, by a mass action effect, reduces the concentration of the reactive species. 

For many elements, the atomization efficiency (the ratio of the number of atoms to the total number of analyte species, atoms, ions and molecules in the flame) is 1, but for others it is less than 1, even for the nitrous oxide-acetylene flame (for example, it is very low for the lanthanides). Even when atoms have been formed they may be lost by compound formation and ionization. The latter is a particular problem for elements on the left of the Periodic Table (e.g. Na Na + e the ion has a noble gas configuration, is difficult to excite and so is lost analytically). Ionization increases exponentially with increase in temperature, such that it must be considered a problem for the alkali, alkaline earth, and rare earth elements and also some others (e g. Al, Ga, In, Sc, Ti, Tl) in the nitrous oxide-acetylene flame. Thus, we observe some self-suppression of ionization at higher concentrations. For trace analysis, an ionization suppressor or buffer consisting of a large excess of an easily ionizable element (e g. caesium or potassium) is added. The excess caesium ionizes in the flame, suppressing ionization (e g. of sodium) by a simple, mass action effect ... 

The reaction is done in water with an excess of OH to drive the reaction forward by the mass action effect. There is another reason too. Think which species will actually be formed in aqueous alkali. 

By driving over an unfavourable equilibrium using the mass action effect. 

The simplest supposition, to make is that the increased concentration in the condensed film brings about increased velocity of reaction in virtue of a purely mass action effect. This theory, however, has been shown in many ways to be untenable. The clearest proof of its inadequacy is afforded by the study of those reactions in which the same substance can undergo transformation in alternative ways. Thus alcohol vapour can suffer decomposition into ethylene and water or into aldehyde and hydrogen according to the equations ... 

Although different increases in the concentration of the alcohol vapour are doubtless produced at the different surfaces, these increases, in so far as they have a simple mass action effect, should operate to exactly the same extent in respect of the alternative reactions, because the rate of each is directly proportional to the concentration of alcohol. Different catalysts would be expected to produce different changes in the total rate of transformation of the reactant, but to be without effect on the relative amounts of the products. 

The amount of decomposition may be decreased by mixing the salt with a small amount of pure ammonium iodide before melting. The ammonia and hydrogen iodide, which result from the thermal decomposition of the ammonium iodide, repress the decomposition of the alkali iodide by a mass-action effect. 

Upset equilibrium systems do increase hydrogen yields but, as yet, kinetic and/or mass action effects limit the viability of such processes. 

In Chapter 13 we saw this way of makings reaction go faster by raising the energy of the starting material. We also saw that the position of an equilibrium can be altered by usinga large excess of one of the reagents. This is sometimes called a mass action effect. 

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