Preparation of a Co-ordination Compound

Preparation of a Co-ordination Compound

Introduction

Coordination chemistry is the study of compounds that form between metal ions and other neutral or negatively charged molecules (AP chemistry lab, 2008). This report discusses an experiment to study the Preparation of a Coordination Compound containing cobalt, chlorine and ammonia and the subsequent determination of the formula of the compound. The compound is prepared by the reaction cobalt (ii) chloride 6 hydrate (), ammonium chloride (), concentrated ammonium water (), charcoal and hydrogen peroxide (). Pentaamminechlorocobalt III chloride is synthesized by reacting concentrated ammonia, Cobalt (II) Chloride Hexahydrate, hydrogen peroxide, and concentrated hydrochloric acid together. The objective is to determine the number of atoms using different methods for each ion.

Materials

Reagents

  • Ammonium chloride
  • Distilled water
  • Cobalt (ii) chloride hexahydrate
  • Cobalt solution
  • Powdered charcoal
  • Concentrated ammonia water
  • Hydrogen peroxide
  • Concentrated hydrochloric acid
  • Silver chloride
  • Silver nitrate
  • Concentrated nitric acid
  • Ethyl

Apparatus

  • Thermometer
  • Glass stirring road
  • Clamp and stand
  • 50 ml, 250 ml and 600 ml beaker
  • Erlenmeyer flask
  • Centigram balance
  • Buchner funnel
  • Filter flask
  • Ice bath
  • Fritted glass filter crucible
  • Spatula

Procedure

Weigh 10g of ammonium chloride on a centigram balance. Add the ammonium chloride to 20ml distilled water in the 50 ml water. Heat the solution until it boils. Add to the boiling solution 15g of cobalt (ii) chloride and record all the masses.

Add hot cobalt solution to the 250 ml Erlenmeyer flask with 1g powdered charcoal. Cool the solution by passing running water. Add 30 ml of concentrated ammonia water to wash any remaining cobalt (ii) solution and transfer it to Erlenmeyer flask.

Cool the flask and its contents to below  in an ice bath. Add carefully 40 ml of hydrogen peroxide to the cobalt (ii) solution in the flask.

Clamp the flask and contents in a 600 ml beaker as water bath. Heat the bath to  maintaing a  more or less variance. Stir the solution with a glass rod, maintaining the same temperature until a pink color appears. Remove the flask and the contents from the water bath once the pink color disappears and cool it to zero degrees.

Filter the crystals formed, retain the residue and discard the filtrate.

Put 125 ml distilled water into a 250 ml beaker and add 5 ml concentrated hydrochloric acid. Heat the solution to boil and transfer the residue to the boiling solution using a spatula.

Upon dissolution filter the hot solution to remove charcoal. Discard the charcoal and save the filtrate.

Add 20 ml of concentrated hydrochloric acid to the filtrate; cool the solution in an ice bath while stirring continuously. At  separate the precipitated crystals and wash the products twice with 15 of 60 by volume ethyl alcohol- water mixture followed by 15 ml by twice 95 by volume of the same.

Discard the filtrate, dry the residue using several thicknesses of filter paper in a watch glass.

Discussion

When the compound is dissolved in water, the free anions go into solution, but the ones in the complex will remain firmly attached to cobalt. They neither will react with a precipitating agent such as Ag+ ion, which tends to form AgCl with any free Cl-ions. All of the NH3 molecules will be in the complex ion, and will not react with added H+ ion, as they would if they were free

The synthesis of the unknown inorganic compound follows this (unbalanced) equation:

CoCl2· 6 H2O(s) + H2O + NH4Cl(s) + NH3        Cox (NH3)zCly(s)+ H2O(l

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Preparation of a Co-ordination Compound

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