Multiple Oxidation States of Transition Elements

PURPOSE OF EXPERIMENT Study properties of aqueous ions representing multiple oxidation states of several transition elements, and determine the identity of two vanadium ions by redox titrations with Mn04 . 

Transition elements make up the lower left-central portion of the periodic table of the elements, bridging the s-block elements at the left and the p-block elements at the right. Five properties are commonly attributed to transition elements (1) they are all metals, (2) many of them form compounds involving a variety of oxidation states, (3) many of them form compounds and aqueous solutions that are colored, (4) many of them form complex ions, and (5) many of them form compounds exhibiting paramagnetic behavior. This experiment involves multiple oxidation states of several transition elements a variety of colored solutions, and several complex ions involving a transition metal cation and oxygen. 

In this experiment you will observe and try to identify qualitatively these ions and their characteristic colors. Your identification is made somewhat more difficult by the fact that mixtures of these ions will produce a great variety of intermediate colors that will not be characteristic of a particular ion. Therefore, you must observe all color changes carefully and take detailed notes so that you can organize and explain your observations meaningfully by the end of the experiment. In addition, you will determine quantitatively the identity of two oxidation states of vanadium by means of redox titrations with Mn04.  

Zinc amalgam is prepared according to the following procedure. Weigh 5.0 g of 20-mesh granular zinc metal on a beam balance (Laboratory Methods C), and place it in a 50-mL Erlenmeyer flask. Add 20. mL of 0.1 M 

Place a few crystals of iron(II) sulfate, FeS04 7H20, in a 10 x 75-itiiti test tube. Then add several drops of water, and stir the solution with a glass stirring rod to dissolve the FeS04 7H20 and produce a solution containing Fe2+ ions (Laboratory Methods K). Describe the color of the Fe2+ solution in TABLE 41.1C. 

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