[Fmeub]

I am not sure what the products are for the two different reactions of tetraamminecarbonatocobalt(III)nitrate with HCl and HNO₃.The tetraamminecarbonatocobalt(III)nitrate is suspended in water and then concentrated HCl is added.

For the second reaction the procedure is repeated for (1:1) concentrated HNO₃ and water and then NaNO₂ is added.

It seems that the diaqua complex is formed if the reaction mixture is cooled in an icebath immediately after the additions, but in this procedure the mixtures were heated on a hotplate at 55-65 degrees Celcius for 30 minutes.

Does [Co(NH₃)₄Cl₂]Cl form in the first case, and maybe [Co(NH₃)₄(OH₂)₂](NO₃)₃ form in the second case?

How can a person know which ligands will replace which other ligands?

[Dolphinsiu]

Firstly, we should write down the half-reaction for conc.HNO₃

NO₃^- + 4H⁺ + 3e^- --> NO₂ + 2H₂O

Then we should know the product will be [Co(NH₃)₄(OH₂)₂]³⁺ after the reaction.

I think for the first case, Co(NH₃)₄Cl₃ is formed

[shelanachium]

You also need to consider whether cis or trans isomers are produced.

[Co(NH3)4CO3]+ is necessarily cis, as the carbonate group acts as a chelator, it binds to two adjacent positions. So simple replacement of carbonate by H2O or Cl- would give the cis isomer (H2O or Cl- in adjacent positions).

However the trans isomers, with H2O or Cl- in opposite positions, are more thermodynamically stable, and will be favoured if the solutions are hot, giving the activation energy to allow the conversion.

If nitrite is added we would expect the cis or trans dinitro complexes [Co(NH3)4(NO2)2]+ to form.