Super HARD Chemistry question lol

Question

What is the coordination number of the complex ion:

Cr w/ two (ammonia), w/ two chlorides, w/ one (oxalate). The ion has an overall charge of negative one.

Cr(NH3)2Cl2(C2O4)-

What would be the charge on the complex if all ligands chloride ions?

Answer 1

Cr(NH3)2Cl2(C2O4)-

NH3 in neutral

Cl- is negative one (-2)

C2O4 is negative two (-2)

Total charge is -4

Therefore if the complex has a charge of -1, then chromium would have to be +3.

The coordination number of Cr would be 6.  (The oxalate is bidentate -- attaches in two places.)

If there were all chloride ions in the complex then the complex ion would be -3.

[CrCl6]^3-

Answer 2

-3: Cl2 and NH3 both have no charge, and oxalate has a -2 charge. That leaves Cr with a +1 charge, and if you replace that with a Cl- ion, you get (-1 - 2) = -3.