Cobalt syntheis

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Synthesis of Cobalt Complex

Morenike Clement

Chemistry 1B Fall 2014 September 23, 2014


Experiment is to synthesize a cobalt complex with a variety of ligands. We first want to oxidize the complex to convert the cobalt metal from 2+ to 3+ oxidation state. For oxidation we used hydrogen peroxide in a basic solution. Next while solution is being heated add concentrated HCl to create a slurry of crystals. Substance will be cooled to room temperature and filtered out using suction filtration with HCl then next ethanol to dry crystal faster. After crystals are dried for an hour, resulting product is weighed. At the end of Part 1 of experiment, weight of substance in grams is 1.687g.


H₂O₂(aq) + 2e¯-----> 2OH¯

2Co²⁺ (aq)------> 2Co³⁺(aq) + 2e¯

2Co³⁺(aq) +12NH₃(aq)------> 2(Co(NH₃)₆)³⁺ (aq)


The purpose of the experiment is to synthesize a cobalt compound containing a choice of ligands such as ammonia, chlorine and ethylenediamine.

Experimental Procedure

1. Add 30mL of 10% solution of ethylenediamine to a solution of 8grams of Cobalt (II) chloride hexahydrate ( CoCl₂ 6H₂O) in 20mL of water in a large evaporating dish.

2. Put dish on a 600mL beaker. 200 to 300mL of water should be at a low boil.

3. Put 6mL of 30%(by mass) of H₂O₂ solution in small amount and mix the solution for 40 minutes, make sure the volume of the solution stays at around 40mL by adding small amounts of water seldomly. CoCl₂ will be oxidized to cobalt (III).

4. Take the cobalt(III) to hood and add 20mL of concentration HCl acid slowly. HCl is very corrosive, so carefully. Continue to heat and stir with no water this time until you see crystal forming. Stopping of evaporation at the right time is vital for success of the synthesization.

5. Cool by...