The oxidation and coordination numbers of cobalt in the compound [Co(NH3)5Cl]Cl2 are, respectively?

Question

a. 2 and 6

b. 2 and 8

c. 3 and 6

d. 3 and 8

e. None of these choices is correct.

Answer 1

[Co(NH3)5Cl]Cl2

The two chloride ions attached to the complex ion tells us that the complex ion has a net charge of +2.

In [Co(NH3)5Cl]^2+ cobalt would have an oxidation number of +3 since ammonia is zero and Cl is -1.  

+3 + (-1) =  +2

Since there are six ligands attached to Co, the coordination number is 6.

Therefore, your answer is (C).