Stoichiometry of reactions in solution

Stoichiometry of reactions in solutions is described by balanced equations that relate the number of moles of each reactant and product. The number of moles of each reaction species in a volume of solution is given by W = M,V. 

I See the Saunders Interactive General Chemistry CD-ROM, Screens 5.13 and 5.15, Stoichiometry of Reactions in Solution. 

So far we have considered the stoichiometry of reactions in solution that result in the formation of a precipitate. Another common type of solution reaction occurs between an acid and a base. We introduced these reactions in Chapter 8. Recall from that discussion that an acid is a substance that furnishes H+ ions. A strong acid, such as hydrochloric acid, HCl, dissociates (ionizes) completely in water. 

Amount-Mass-Number Conversions Involving Solutions 100 Diluting a Solution 100 Stoichiometry of Reactions in Solution 103... 

Most reactions in the general chemistry laboratory are carried out in solution. This is partly because mixing the reactants in solution helps to achieve the close contact between atoms, ions, or molecules necessary for a reaction to occur. The stoichiometry of reactions in solutions can be described in the same way as the stoichiometry of other reactions, as we saw in Example 4-6. A few new ideas that apply specifically to solution stoichiometry are also helpful. 

Many environmental reactions and almost all biochemical reactions occur in solution, so an understanding of reactions in solution is extremely important in chemistry and related sciences. We ll discuss solution chemistry at many places in the text, but here we focus on solution stoichiometry. Only one aspect of the stoichiometry of dissolved substances is different from what we ve seen so far. We know the amounts of pure substances by converting their masses directly into moles. For dissolved substances, we must know the concentration—the number of moles present in a certain volume of solution—to find the volume that contains a given number of moles. Of the various ways to express concentration, the most important is molarity, so we discuss it here (and wait until Chapter 13 to discuss the other ways). Then, we see how to prepare a solution of a specific molarity and how to use solutions in stoichiometric calculations. 

When reactions occur in solution, reactant and product amounts are given in terms of concentration and voiume. Moiarity is the number of moles of solute dissolved in one liter of solution. Using molarity as a conversion factor, we apply the principles of stoichiometry to all aspects of reactions in solution. 

Solution Stoichiometry Quantitative studies of reactions in solution require that we know the concentration of the solution, which is usually represented by the molarity unit. These studies include gravimetric analysis, which involves the measurement of mass, and titrations in which the unknown concentration of a solution is determined by reaction with a solution of known concentration. 

By using molarity as a conversion factor, we can apply the principles of stoichiometry to reactions in solution. 

Distinguish between an electrolyte and a nonelectrolyte, and provide examples of each. 5.2 Use the solubility guidelines tor common ionic solids to determine whether 5-4 Oxidation-Reduction Reactions Some General Principles 5-7 Stoichiometry of Reactions in Aqueous Solutions Titrations... 

Stoichiometry of Reactions in Aqueous Solutions Titrations— A common laboratory technique applicable to precipitation, acid-base, and redox reactions is titration. The key point in a titration is the equivalence point, which can be observed with the aid of an indicator. Titration data can be used to establish a solution s molarity, called standardization of a solution, or to provide other information about the compositions of samples being analyzed. 

Bromine readily adds across an alkenic double bond by electrophilic addition (Figure 8.4). The brominated compound is usually colourless, but bromine in solution ( bromine water ) has a red colour. Addition of bromine water to an aikene is accompanied by a loss of the red colour as reaction proceeds. The stoichiometry of reaction is almost always 1 1, with one molecule of bromine reacting per double bond. 

Another term used to describe rate processes is molecu-larity, which can be defined as an integer indicating the molecular stoichiometry of an elementary reaction, which is a one-step reaction. Collision theory treats mo-lecularity in terms of the number of molecules (or atoms, if one or more of the reacting entities are single atoms) involved in a simple collisional process that ultimately leads to product formation. Transition-state theory considers molecularity as the number of molecules (or entities) that are used to form the activated complex. For reactions in solution, solvent molecules are counted in the molecularity, only if they enter into the overall process and not when they merely exert an environmental or solvent effect. 

Solution The stoichiometry of Reaction 6-19 tells us that H and OH are produced in a 1 1 molar ratio. Their concentrations must be equal. Calling each concentration x, we can write... 

Preferred conditions for the reaction of the zeolite with the metal ammonium fluoride are as follows. A zeolite-water slurry containing about 10-25 gm of zeolite per 100 cm3 of water is preheated to 75-95°C. When substituting Ti, the titanium salt is added to the zeolite as a water slurry containing finely divided crystals, 10 gm of (NH4>2T1F6 per 100 cm3 of water. With iron substitution, the iron salt, when added as (NH4>3FeF6, is added from a 10 wt.% solution of the salt in water. Alternatively, FeF3 can be added to a solution of NH4HF2 or NH F such that the stoichiometry of fluorine (F2) to Fe3+ is 3.0 and the total amount of salt in solution is about 10 wt.%. The addition rate of the metal ammonium fluoride salt to the zeolite slurry is about 0.005 moles of the metal ion per minute per mole of aluminum in the zeolite. 

Simple 2,2-dibutyl-l,3,2-dioxastannolanes form solid complexes of monomer units with certain nucleophiles, such as pyridine and dimethyl sulfoxide, that have 1 1 stoichiometry and pentacoordinate tin atoms.62 Such complexes are less stable for more-substituted stannylene acetals, such as those derived from carbohydrates.62 Unfortunately, the precise structures of these complexes have not yet been defined. Addition of nucleophiles to solutions of stannylene acetals in nonpolar solvents has been found to markedly increase the rates of reaction with electrophiles,63 and transient complexes of this type are likely intermediates. Similar rate enhancements were observed in reactions of tributylstannyl ethers.57 Tetrabu-tylammonium iodide was the nucleophile used first,57 but a wide variety of nucleophiles has been used subsequently tetraalkylammonium halides, jV-methylimidazole,18 and cesium fluoride64,65 have been used the most. Such nucleophilic solvents as N,N-dimethylformamide and ethers probably also act as added nucleophiles. As well as increasing the rates of reaction, in certain cases the added nucleophiles reverse the regioselectivity from that observed in nonpolar solvents.18,19... 

While studies on the crystal structures of RE(III)-amino acid complexes can give us clear pictures on the ways in which RE(III) ions and the amino acids bond to each other, their solution chemistry, which deals with the reactions in solution, the chemical species formed, their stability, as well as their distribution over certain pH ranges, can help us understand better the in vivo behaviors of RE(III) ions and their complexes with amino acids. Work on the solution chemistry of RE-amino acid complexes has been carried out since the early 1960s [9]. It has been found that the amino acids studied behave very similarly to one another, just as we have learned from their structural chemistry. Mononuclear species with 1 1 and 1 2 (RE L) stoichiometry have been reported for all of the amino acids. In some studies, the presence of mononuclear species with stoichiometry 1 3, dinuclear species with stoichiometry 2 4 and 2 6, in addition to the hydrolyzed species, such as [RE(OH)L]+, [RE(OH)] +, and RE(OH)3(s), have been confirmed [126, 135, 136]. 

The data have been reconsidered by the review and the following observations were made, see also Appendix A. The solid selenium used in the experiments was obtained by reduction of a selenite solution by thiosulphate. The selenium might therefore not be in its standard state. The activity of the specimen is most likely elose enough to the standard state activity, however, since the precipitate was kept at boiling temperature for several hours. A recalculation of the side-reactions with more recent values of the auxiliary equilibrium constants made little difference to the result. The analytical data are not always consistent with the stoichiometry of Reaction (V.24) and the known initial composition of the test solution. The authors also observed this and held oxidation of iodide by initially present oxygen responsible for the discrepancies. Flowever, in some instanees the deviations from the expected concentrations are remarkably large. The deviations do not invalidate the results if equilibrium prevails, which was tested. 

---