Describe the preparation of the ammonium carbonate/ammonia mixture. Describe wha

Question

Describe the preparation of the ammonium carbonate/ammonia mixture. Describe what you observed upon combining this solution with the cobalt solution. Write a reaction along the lines given in the text to show the expected cobalt containing species present in the solution at this point.

Procedure

Carbonatotetraamminecobalt (III) Nitrate, [Co(NH3)4CO3]NO3: dissolve 20 g (0.21 mol) of (NH4)2CO3 in 60 mL of H2O and add 60 mL of concentrated aqueous NH3 (do not worry if all the (NH4)2CO3 does not dissolve in the water as it will dissolve when the ammonium hydroxide is added). While stirring, pour this solution into a solution containing 15 g (0.052 mol) of [Co(OH2)6](NO3)2 in 30 mL of H2O. Then slowly add 8 mL of a 30 % H2O2 solution (the 8mL should be added to the cobalt/ammonia solution 1mL at a time with stirring - there is a delayed release of the gas which can cause the solution to foam-over if the hydrogen peroxide is added all at once). Pour the solution into a large beaker and place on a hot plate underneath a fume cap. Heat the solution to evaporate the solvent until only ~100 mL is left - the solution temperature may be raised to the 80-85°C range without the risk of decomposing the cobalt-ammine complex you are trying to isolate. However, above 90°C and particularly near the boiling point decomposition

Explanation / Answer

When you combine ammonia/ammonium carbonate solution to cobalt, [Co(NH3)4CO3]NO3 will form along with CO2 gas. Due to the formation of this gas, effervescence will be observed. The reaction is

Co(NO3)2 + NH3 + (NH4)2CO3 + H2O2 ----> [Co(NH3)4CO3]NO3 + NH4NO3 + H2O

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