32 Synthesis of Some Coordination Compounds Some of the most interesting researc

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32 Synthesis of Some Coordination Compounds Some of the most interesting research in inorganic chemistry has involved the preparation and study of the properties of those substances known as coordination compounds. These com- pounds, sometimes called complexes, are typically salts that contain complex ions. A complex ion is an ion that contains a central metal ion to which are bonded small polar molecules or simple ions the bonding in the complex ion is through coordinate covalent bonds, which ordinarily are rela tively weak In this experiment we shall be concerned with the synthesls of two coordination compounds A. [Cu/NH,)so, H,O B [Co(NH,)] Cl The complex ions in these substances are enclosed in brackets to indicate those species which are bonded to the central ion. In this experiment you will prepare the complex ions by making use of reactions in which substituting ligands, or coordinating species, replace other ligands on the central ion. The reactions will usually be carried out in water solution, in which the metallic cation will initially be present in the simple hydrated form; addition of a reagent containing a complexing ligand will result in an exchange reaction of the sort Cu(H2O)42 +(aq) + 4 NHfaq)= Cu(NHJ2+(aq) + 4H20 In many reactions involving complex ion formation the rate of reaction is very rapid, so that the thermodynamically stable form of the ion is the one produced. Such reactions obey the law of chemical equilibrium and can thus be readily controlled as to direction by a change in the reaction conditions. Reaction 1 proceeds readily to the right in the presence of NH, in moderate concentra tions. However, by decreasing the NH, concentration, for example by the addition of acid to the system, we can easily regenerate the hydrated copper cation. Complex ions that undergo very fast exchange reactions, such as those in Reaction 1, are called labile. Most but by no means all complex ions are labile. Some complex ions, including one to be studied in this experiment, will exchange ligands only slowly. For such species, called inert or nonlabile, the complex ion produced in a substitution reaction may be the one which is kinetically rather than thermodynamically favored. Alteration of reaction conditions, perhaps by the addition of a catalyst, may change the relative rates of formation of possible complex products and so change the complex ion produced in the reaction. In your experiment you will use a catalyst, activated charcoal, in the preparation of the complex ion in compound B. In the absence of the catalyst the complex ion that would form would be Co(NH3) H203+. The Co(III) present in these species is stabilized in complex ions containing NHs ligands. determine whether a complex ion is labile is to note whether a color change occurs in a solution containing the ion when a good complexing ligand is added. You may wish to use this procedure in Many complex ions are highly colored, both in solution and in the solid salt. An easy way to observing relative rates of substitution reactions involving the complex ions you prepare.

Explanation / Answer

Amounts of products calculated from the complete reaction of the limiting reagent is called theoretical yields

here

A ) [Cu(NH3)4]SO4*H2O

Therefore the number of moles of Cu(SO4).5H2O you started of with is:  250 g mol-1
7/250= 0.028

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