## HW 17.31 b

Sue Xu 2K
Posts: 58
Joined: Fri Sep 29, 2017 7:06 am

### HW 17.31 b

It asks for the formula of pentaamminesulfatocobalt(III) chloride. Is the answer wrong? I think it's [Co(NH3)5(SO4)]Cl3 since it said the (III).

Amanda Mac 1C
Posts: 58
Joined: Fri Sep 29, 2017 7:05 am

### Re: HW 17.31 b

I think the (III) refers to the Cobalt and not the chloride. So your formula is correct, just take out the subscript 3 on the Cl.

Isaac Eyler 1E
Posts: 12
Joined: Fri Sep 29, 2017 7:04 am

### Re: HW 17.31 b

I was wondering about this too, but I read another post addressing this issue and the way I understand it now is that the sum of the charges of atoms inside the brackets will be opposite of the charge of the atom on the outside of the brackets. (Someone correct me if I'm wrong, or phrasing it wrong).

On the inside of the brackets:
Co: the III given results in a +3 charge
(NH3)5: NH3 is a neutral ligand so..... (5)(0) = 0
(SO4): SO4 has a charge of -2 so..... (1)(-2) = -2

If you add these up you get +1 inside the brackets... therefore you must have the opposite, -1, on the outside of the brackets.

Therefore, you only need one chlorine atom on the outside to achieve the balancing -1 charge.

AtreyiMitra2L
Posts: 169
Joined: Fri Sep 29, 2017 7:03 am
Been upvoted: 1 time

### Re: HW 17.31 b

Cobalt does have an oxidation number of +3. However, the oxidation number of sulfato is -2. 3-2 means the coordination sphere has an overall charge of +1

aaron tang 2K
Posts: 49
Joined: Thu Jul 27, 2017 3:01 am

### Re: HW 17.31 b

The answer that is provided through solutions manual is correct because Cobalt has an oxidation number of 3+ and Sulfate has an oxidation number of 2-, which means the overall oxidation number is 1. So it is [Co(NH3)5(SO4)]Cl