Transition metal complexes

During this experiment we will see a range of transition metals formed by copper and cobalt ions.

Complexes of cobalt


Place 3ml of 0.5M cobalt(II)chloride into a small test tube. Most of the ions in solution should be Co(H2O)6+2 . Notice the colour of the solution.

Now add 3ml of saturated NaCl solution and heat the mixture over a bunsen flame. Most of the ions are now CoCl4-2 . Note the colour change. Click to see 120kb movie. of the colour change.

Now cool the mixture under running water and once again notice the colour change.

 

What is the equilibrium expression for the reaction involving CoCl4-2 and Co(H2O)6+2 ?

Solution


Is the forward reaction exothermic or endothermic? Explain. Think of the colour change that occured when the solution was heated.

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