Reaction unit

The number of equivalents, n, is based on a reaction unit, which is that part of a chemical species involved in a reaction. In a precipitation reaction, for example, the reaction unit is the charge of the cation or anion involved in the reaction thus for the reaction... 

The moles of a species that can donate one reaction unit. 

A reaction unit is that part of a chemical species involved in a reaction. Consider, for example, the general unbalanced chemical reaction... 

Conservation of reaction units requires that the number of reaction units associated with the reactant A equal the number of reaction units associated with the reactant B. Translating the previous statement into mathematical form gives... 

Number of reaction units per A X moles A = number of reaction units per B X moles B... 

If we know the moles of A and the number of reaction units associated with A and B, then we can calculate the moles of B. Note that a conservation of reaction units, as defined by equation 2.3, can only be applied between two species. There are five important principles involving a conservation of reaction units mass, charge, protons, electron pairs, and electrons. 

The easiest principle to appreciate is conservation of mass. Except for nuclear reactions, an element s total mass at the end of a reaction must be the same as that present at the beginning of the reaction thus, an element serves as the most fundamental reaction unit. Consider, for example, the combustion of butane to produce CO2 and H2O, for which the unbalanced reaction is... 

All the carbon in CO2 comes from the butane, thus we can select carbon as a reaction unit. Since there are four carbon atoms in butane, and one carbon atom in CO2, we write... 

Hydrogen also can be selected as a reaction unit since all the hydrogen in butane ends up in the H2O produced during combustion. Thus, we can write... 

Conservation of mass also can, with care, be applied to groups of atoms. For example, the ammonium ion, NH4, can be precipitated as Fe(NH4)2(S04)2 6H2O. Selecting NH4 as the reaction unit gives... 

The stoichiometry between two reactants in a precipitation reaction is governed by a conservation of charge, requiring that the total cation charge and the total anion charge in the precipitate be equal. The reaction units in a precipitation reaction, therefore, are the absolute values of the charges on the cation and anion that make up the precipitate. Applying equation 2.3 to a precipitate of Ca3(P04)2 formed from the reaction of Ca and P04 , we write... 

In an acid-base reaction, the reaction unit is the proton. For an acid, the number of reaction units is given by the number of protons that can be donated to the base and for a base, the number of reaction units is the number of protons that the base can accept from the acid. In the reaction between H3PO4 and NaOH, for example, the weak acid H3PO4 can donate all three of its protons to NaOH, whereas the strong base NaOH can accept one proton. Thus, we write... 

Care must be exercised in determining the number of reaction units associated with the acid and base. The number of reaction units for an acid, for instance, depends not on how many acidic protons are present, but on how many... 

In a complexation reaction, the reaction unit is an electron pair. For the metal, the number of reaction units is the number of coordination sites available for binding ligands. For the ligand, the number of reaction units is equivalent to the number of electron pairs that can be donated to the metal. One of the most important analytical complexation reactions is that between the ligand ethylenediaminetetracetic acid (EDTA), which can donate 6 electron pairs and 6 coordinate metal ions, such as Cu thus... 

N number of transfer or reaction units kjaL/( .v ) for external mass... 

Asymptotic Solution Rate equations for the various mass-transfer mechanisms are written in dimensionless form in Table 16-13 in terms of a number of transfer units, N = L/HTU, for particle-scale mass-transfer resistances, a number of reaction units for the reaction kinetics mechanism, and a number of dispersion units, Np, for axial dispersion. For pore and sohd diffusion, q = / // p is a dimensionless radial coordinate, where / p is the radius of the particle, if a particle is bidisperse, then / p can be replaced by the radius of a suoparticle. For prehminary calculations. Fig. 16-13 can be used to estimate N for use with the LDF approximation when more than one resistance is important. 

K Rate coefficient Units dependent on order of reaction Units dependent on order of reaction... 

Central part of this reaction unit is a split-recombine chip micro mixer made of silicon based on a series of fork-like channel segments [32-36]. Standard silicon micro machining was applied to machine these segments into a silicon plate which was irreversibly joined to a silicon top plate by anodic bonding (Figure 4.16). 

In the multi-channel version comprising 10 packed-bed reactors (Figure 5.14), the gas flow is distributed by star-type manifolds to the 10 reaction units [11,12],... 

Owing to the planar layer structure of most micro reactors, uniform illumination is yielded in addition, which can be maintained on increasing throughput by numbering-up [6]. Here, the individual reaction units are assembled in parallel again on a plane, but a larger one. 

Maintenance and Stores Building. The most significant additional risk for occupants of the maintenance and stores building is an explosion from the cycle gas and reaction unit The following action was considered ... 

Experts also disagree on how easily electrochemical processes can be scaled up from laboratory to plant scale. Some see electrochemical processes limited in that the scale is only the two-dimensions based on the electrode surface area, whereas conventional catalytic processes are scaled in three dimensions based on the volume of the reaction unit [48],... 

In the late 1990 s, Foil et al.40-43 proposed the current burst theory. The basic hypothesis is that the electrochemical reactions involved in the dissolution of the silicon surface operate in microscopic units. These reaction units have a temporal and a spatial distribution in number and in the state of activity. The formation of pores is due to the synchronization of these operation units at certain time and geometrical scales. 

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