Which coordinate compound from following has a net negative charge on complex ion?

Which coordinate compound from following has a net negative charge on complex ion?
  1. Tris(ethylene diammine) cobalt(III) chloride
  2. Potassium trioxalato aluminate(III)
  3. Tetracarbonyl Nickel(0)
  4. Diammine silver(I)chloride

Solution

$\mathrm{K}_{3}\left[\mathrm{Al}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right] \longrightarrow 3 \mathrm{~K}^{+}+\left[\mathrm{Al}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)\right]^{3-}$

Asked in: MHT CET 2020 (19 Oct Shift 1)

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