Synthesis of [Co(NH3)4CO3]NO3, adding additional ammonium carbonate reaction? He

Question

Synthesis of [Co(NH3)4CO3]NO3, adding additional ammonium carbonate reaction?

Here is the background information:

Objective: To prepare and isolate a coordination complex of the Co^3+ via oxidation of a Co^2+ salt. The solid is also to be used in additional experiments involving synthesis, conductivity, UV-Vis, and infrared spectroscopy.

Observe that:

The synthesis of [Co(NH3)4CO3]NO3 will be carried out according to the unbalanced equation below:

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

The Co(NO3)2 that is available commercially has the formula Co(NO3)2 . 6 H2O and very probably is a coordination compound having the ionic formulation [Co(OH2)6](NO3)2. Since Co(II) complexes, like those of Ni(II), react very rapidly by ligand exchange, the first step in the reaction might be expected to be,

Co(OH2)6^(2+) + 4 NH3 + CO3^(2-) --> Co(NH3)4Co3 + 6 H2O

This Co(II) complex could then be oxidized by the transfer of an electron to H2O2 to give the relatively non-reactive Co(III) ion, [Co(NH3)4CO3]^+

The preparation of [Co(NH3)5Cl]^(2+) is accomplished from the carbonate complex according to the following series of equations:

[Co(NH3)4CO]^+ 2 HCl-->[Co(NH3)4(OH2)Cl]^(2+) + CO2 (g) + Cl^-

[Co(NH3)4(OH2)Cl]^(2+) + NH3 (aq) --> [Co(NH3)5(OH2)]^(3+) + Cl^-

[Co(NH3)5(OH2)]^(3+) + 3 HCl --> [Co(NH3)5Cl]Cl2 + H2O + 3H^+

Here is the question:

After adding water to Cobalt (II) Nitrate Hexahydrate, Nh3 and ammonium carbonate is added to the cobalt solution. The solution is heated and H2O2 is added to oxidize the Co. After, ammonium carbonate is continually added to the solution and effervescence is observed.

Why is additional ammonium carbonate added? Offer a reaction which would account for this and the probable identity of the gas.

I think that CO2 is produced during this time but I am not sure what the reaction would be. Thanks.

Experiment 4 Part A Part A: Synthesis of ICo(NH3) COPINO3 Objective: To prepare and isolate a coordination complex of the Co via oxidation of a Co salt. synthesis, conductivity, UV-Vis. also to be used in additional experiment ts involving and infrared spectroscopy. Pre-Lab Study: The only equation you need to include in your Pre-lab for Exp. 4a is the first cquation listed below @-however you must balance the equation. Backg round. of particular importance to the development of coordination chemistry are metal xes of the type o be synthesized and characterized in this experiment. Prior to 1950, research in this area was almost exclusively concerned with the investigation of complexes of transition metal ions with such monodentate ligands as CI Br T, NH3, pyridine, CN and NOi and bidentate ligands as ethylenediamine (H2NCHICHINHr. oxalate CO2CCO2 glycinate (H2NCH CO2 and COs T. These complexes form the basis of a vast amount of research today despite the more recent discoveries of the ligand properties of H, CH, CO, H20 CH2, and benzene, to mention a few. Coordination compounds of Co(TID and Cr(ITD have been of particular interest because their complexes undergo ligand exchange very slowly compared with complexes of many other transition metal ions. For example, Ni(NH) 2* reacts instantaneously with H20 to form Ni(H20) 2+ Under the same conditions, the anal reactions of CoONHs)? and CroNH) occur very slowly. This difference in behavior of complexes of different metal ions has been qualitatively accounted for by ligand field theory and molecular orbital theory. The slow reactivity of Co(II) complexes has made them suitable for extensive investigations. The structures of the octahedral Co(II) complexes which you will prepare are given below. H3N H3N NH3. O NO3 ...Co. NH3 NH3 One important method of characterizing ionic substances is the determination of the ability their solutions to conduct an electric current. Those substances whose solutions have the high conductivity consist of the greatest number of ions. Thus, a one molar solution [Co(NHuDecoolNO will have a lower conductance than a solution of Co(NH CllCl of the sam

Explanation / Answer

ANSWER:

The ammonium carbonate {(NH4)2CO3} added is consumed by Co(II) to form the complex. At the moment when all Co(II) will be consumed (NH4)2CO3 will undergo decomposion under heating producing CO2 gas. The production of CO2 gas is the indication of completion of reaction, that is why we add additional NH4)2CO3.

(NH4)2CO3 (s) -------> 2NH3 (g) + CO2 (g) + H2O(g)

The reaction can be shown to take place in two steps as follows:

(NH4)2CO3 (s) -------> NH4HCO3 (s)+ NH3 (g)

NH4HCO3 -----------> NH3 (g) + CO2 (g) + H2O(g)

The over all reacton is shown above.

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