C. Electrolysis of their aqueous solution

Electrolysis is a process that involves the decomposition of a compound by passing an electric current through its aqueous solution. This process can be used to distinguish between isomeric complexes [Co(NH3)6][Cr(NO2)6] and [Cr(NH3)6][Co(NO2)6].

Here's how the electrolysis of their aqueous solutions can help to distinguish between these two complexes:

1. Setup:
- Prepare two separate electrolytic cells, each containing the respective isomeric complex solution.
- Connect the positive terminal of a power supply to the anode (positive electrode) of one cell and the negative terminal to the cathode (negative electrode) of the other cell.
- Connect the negative terminal of the power supply to the cathode of the first cell and the positive terminal to the anode of the second cell.
- Place appropriate electrodes (such as platinum or carbon) in each cell, ensuring they do not touch each other.

2. Electrolysis process:
- When the electric current is passed through the solution, the anode of one cell will undergo oxidation, while the cathode of the other cell will undergo reduction.
- In the case of [Co(NH3)6][Cr(NO2)6], the Co(III) ion is reduced at the cathode, and Cr(III) ion is oxidized at the anode.
- In the case of [Cr(NH3)6][Co(NO2)6], the Cr(III) ion is reduced at the cathode, and Co(III) ion is oxidized at the anode.

3. Observation:
- Since Co(III) ions are easier to oxidize than Cr(III) ions, the electrolysis of [Co(NH3)6][Cr(NO2)6] solution will result in the formation of Co(II) ions at the anode and Cr(IV) ions at the cathode.
- On the other hand, the electrolysis of [Cr(NH3)6][Co(NO2)6] solution will result in the formation of Cr(II) ions at the cathode and Co(IV) ions at the anode.
- The presence of different oxidation states of the metal ions can be confirmed by performing appropriate chemical tests or by analyzing the electrolysis products.

By analyzing the products of electrolysis, it is possible to differentiate between [Co(NH3)6][Cr(NO2)6] and [Cr(NH3)6][Co(NO2)6]. This method takes advantage of the different redox behaviors of the metal ions in the two complexes.