Dear Chegg, I have to identify an unknown inorganic compound (salt containing aq

Question

Dear Chegg, I have to identify an unknown inorganic compound (salt containing aqua complex) by using following spectrums as shown down below:
According to a table that my teacher has given me and also according to the UV-VIS spectra as shown down below.. I can see that my transition metal-ion is: Co2+ .. Cuz of the wavelength 511nm. > close to 512nm for the higest peak.

And now by using both the UV-Vis spectra as shown earlier and this IR-spectra as shown down below.. I have to identify which one of these counter ions I have in my salt: BF4- , SiF62- , NO3- , SO42- , ClO4- , or CH3COO-. and also how many H2O ligands I have in my transition metal complex.

Hope someone can help.. Cuz it's really important and I know it's kinda a big question to answer.. but any help would be appreciated :) Thanks for reading. and my unknown compound (salt) had this color: Solution:

*ADDITION*
Someone on Chegg gave me this solution, but I need a step by step solution.. I mean how the datas (spectrums) are analyzed and used to get the following solution..:
After analysing your datas and referring with literatures for the color of the salt it is found to be Cobalt(II) acetate (Co(CH3COO)2.4H2O) total of 4 water ligand presence.

Explanation / Answer

From UV spectrum, you came to know that it is Co2+ metal ion because it showed a peak at 511 nm.

Next from IR spectrum, we can see a strong peak at around 1600 cm-1. This peak is characteristic of C=O stretching. C-O shows a peak at around 1000-1150 cm-1. This peak is also present in the IR spectrum. A broad peak at 3500 nm is a sign of presence of O-H group or water molecules. As acetate group contains both C=O and C-O bonds, so we can say that acetate as well as water molecules are present in the compound.

Next is by appearance of the compound, the compound is reddish pink in colour and not a free flowing powder. The pink colour is due to the Co2+ transition metal ion and it is not flowing powder because of the presence of water molecules. Co(II)acetate compound commonly exists as tetrahydrate. Two acetate ions would be there to neutralise the Co2+ charge. So, the formula of the compound is Co(CH3COO)2.4H2O and is an octahedral complex.

I hope now it is clear.

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