Synthesis of [Co(NH 3 ) 6 ] 3+ and [Co(NH 3 ) 5 Cl] 3+ The two metal complexes p
ID: 903153 • Letter: S
Question
Synthesis of [Co(NH3)6]3+ and [Co(NH3)5Cl]3+
The two metal complexes produced in class both start with CoCl2·6H2O which is substituted by NH3 supplied by ammonium chloride, NH4Cl, and aqueous ammonia, NH4OH. For the 2nd complex concentrated HCl is added which substitutes one of the NH3 ligands with Cl-. After the Co2+ complexes are prepared 30% hydrogen peroxide, H2O2, oxidizes the metal in the complex to Co3+.
(a) Write out the balanced reactions for the preparation of the two cobalt complexes
(b) determine the limiting reagent and the predicted yield for both reactions (concentrated ammonium hydroxide is 14.5 M)
Explanation / Answer
a) 4 CoCl2.6H2O + 4NH4Cl +20NH3 + O2 ----------> 4 [Co(NH3)6]Cl + 8H2O
b) for 1st complex yield is low.limiting reagents are CoCl2.6H2O & NH4Cl
a)2 CoCl2.6H2O + 2 NH4Cl + H2O2 + 8 NH4OH = 2 [Co(NH3)5Cl]Cl2 + 22 H2O
b)yield is high ,.limiting reagents are CoCl2.6H2O & NH4Cl
The limiting reagent is the reactant that is completely used in a reaction, and can be determine when the reaction is completed.
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