Question

What is the charge on the complex ion in `Ca_2[Fe(CN)_6]`?

Answer 1

As written, you have an `[Fe(C-=N)_6]^(-4)` complex ion.

Explanation:

Calcium metal typically forms the `Ca^(2+)` ion. If this is a real compound (and not a typo), you thus have a `Fe(II+)` centre. The charge of the complex as written is of course zero. Why?

I would check your source.