[Radu]

  oblem 6. Transition metal compounds
Procedures for the synthesis of several compounds of transition metal X are given below.
“A solution of 2 g of very fine powder A in 50 mL of 28% sodium hydroxide is triturated in a small Erlenmeyer flask with 3.5 g of finely ground Na2SO3·7H2O; the flask stands in an ice bath. The trituration requires about 10 minutes, that is, until a light-blue crystalline slurry is obtained. The mixture is then transported under vacuum onto an ice-cooled glass filter, and the product washed thoroughly with 28% sodium hydroxide at 0°C. The wet preparation is rapidly spread in a thin layer on fresh clay and stored at 0°C in an evacuated desiccator (no drying
IChO-2013 Preparatory Problems
13
agent)… The preparative procedure should be designed so as to avoid contamination by silicates or aluminates … Product B, in the form of well-crystallized sky-blue rods, remains stable at 0°C if kept free of H2O and CO2… A solution of B in 50% potassium hydroxide turns grassy green upon heating or dilution; simultaneously, C is precipitated.
In a pure form, salt D, which is a main constituent of B, is prepared according to the following procedure: «NaOH is entirely dehydrated by heating in silver pot at 400ºС and mixed with C in a such way that Na : X molar ratio is 3 : 1. Mixture is heated to 800ºС in a silver pot and kept under oxygen flow for 5 h. The formed product D is rapidly cooled to room temperature». Salt D is a dark-green compound inert to CO2.
A solution of 30 g of KOH in 50 mL of water is prepared; 10 g of А is added and the mixture is boiled in an open 250-mL Erlenmeyer flask until a pure green solution is obtained. The water lost by evaporation is then replaced and the flask set in ice. The precipitated black-green crystals, which show a purplish luster, are collected on a Pyrex glass filter, washed (high suction) with some 1 M potassium hydroxide, and dried over P2O5. The formed compound E can be recrystallized by dissolving in dil. KOH and evaporated in vacuum».
1. Determine the element Х and molecular formulae of A-Е using the following data: a) sodium weight content in В is 18.1%; b) the weight content of the element Х in А, В, С, D, and Е is 34.8, 13.3, 63.2, 29.3, and 27.9% respectively.
2. Write all the reaction equations.     


please, can anyone tell me first which metal is? i think it's vanadium, but I can't match those mass percentages with the compounds....