Reactions with one reactant

Second-Order Batch Reactions with One Reactant. We choose to write the stoichiometric equation as... 

For a second-order reaction with one reactant, SI a = —ka. Equation (1.49) becomes a quadratic in The solution is... 

This class is the simplest of all micro reactors and certainly the most convenient one to purchase, but not necessarily one with compromises or reduced fimction. HPLC or other tubing of small internal dimensions is used for performing reactions. There are many proofs in the literature for process intensification by this simple concept. As a micro mixer is missing, mixing either has to be carried out externally by conventional mini-equipment or may not be needed at all. The latter holds for reactions with one reactant only or with a pre-mixed reactant solution, which does not react before entering the tube. 

This reactor concept is genericaUy similar to [R 4] and uses the same fabrication and assembly techniques, so the reader is referred to the corresponding description [19]. However, it has only one micro channel as it serves for transporting one liquid (or solution) only, i.e. was constructed for reactions with one reactant only such as eliminations [19]. 

Consider a constant-density reaction with one reactant, A - products, as illustrated for a liquid-phase reaction in a CSTR in Figure 3.6. One experiment at steady-state generates one point value of (—rA) for the conditions (cA, q, T) chosen. This value is given by the material balance obtained in Section 2.3.2 ... 

The following example illustrates a combination of semibatch and semicontinuous operation for an irreversible reaction, with one reactant added intermittently and the other flowing (bubbling) continuously, that is, a combination of Figures 12.3(a) and 12.4(a). Chen (1983, pp. 168-211, 456-460) gives several examples of other situations, including reversible, series-reversible, and series-parallel reactions, and nonisothermal and autothermal operation. 

The same general conclusions apply since backmixing of products with reactants should be avoided, a tubular plug-flow reactor or a batch reactor is preferred. However, there is one respect in which a series reaction involving a second reactant B does differ from simple series reaction with one reactant, even when the orders are the same. This is in the stoichiometry of the reaction the reaction cannot proceed completely to the product Q, even in infinite time, if less than two moles... 

There are two types of catalysts Homogeneous catalysts are in the same physical phase as the reactants. Biological catalysts are called enzymes, and most of them are homogeneous catalysts. A typical homogenous catalytic reaction mechanism involves an initial reaction with one reactant followed by a reaction with a second reactant and release of the catalyst ... 

Typical orders for reactions with one reactant are 0, I, and 2. Fractional values are also common. 

Reactions with One Reactant. If there is only one reactant, there are a limited number of possible reaction types. In aqueous solution, a disproportionation reaction is possible for an element, an oxo ion (Table IV), a simple ion, or a compound. A compound can also undergo a decomposition reaction of various types, as listed in Table I. An ionic compound can undergo an internal redox reaction, in which the oxidant and reductant are chemically combined in a single reactant. An ionic species (Table IV) or a polyatomic salt (or polyatomic anion) can undergo hydrolysis in aqueous solution. 

Second-Order Batch Reactions with One Reactant... 

An nth-order chemical reaction with one reactant obeys the differential equation... 

EXAMPLE 11.11 The following is a fictitious set of data for the concentration of the reactant in a chemical reaction with one reactant. Determine whether the reaction is first, second, or third order. Find the rate constant and the initial concentration. 

For a second-order reaction with one reactant, we have... 

Some techniques for determination of the rate law involve comparison of the integrated rate equation with experimental data on the concentration of a reactant. The method of initial rates allows direct comparison of the differential rate law with the experimental data. In the method of isolation, the concentration of one reactant is made much smaller than the concentrations of the other reactants. During the reaction, the fractional changes in the larger concentrations are negligible, and the small concentration behaves like the concentration in a reaction with one reactant. 

Reactions with One Reactant in Limited Supply. In the previous chemical reactions we assumed that the reactants were completely consumed. No reactant was left when the reaction was over. However, that is usually not the case when chemists carry out an actual synthesis in a laboratory or in industry. 

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