Which among the following is a correct formula of Pentammine aqua cobalt (III) iodide?

Which among the following is a correct formula of Pentammine aqua cobalt (III) iodide?
  1. $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{H}_{2} \mathrm{O}\right)\right] \mathrm{I}_{3}$
  2. $\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)\left(\mathrm{NH}_{3}\right)_{5} \mathrm{I}\right]$
  3. $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{I}\right] \mathrm{H}_{2} \mathrm{O}$
  4. $\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)\left(\mathrm{NH}_{3}\right)_{5}\right] \mathrm{I}$

Solution

Amine $\left(\mathrm{NH}_{3}\right)$ and aqua $\left(\mathrm{H}_{2} \mathrm{O}\right)$ are neutral ligands. Oxidation state of $\mathrm{Co}$ is $+3$. Hence correct formula is $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{H}_{2} \mathrm{O}\right)\right] \mathrm{I}_{3}$

Asked in: MHT CET 2020 (13 Oct Shift 1)

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