The Student Room Group
well you know it has to add up to zero because it is a metal.
what are the oxidation states of chlorine, nitrogen and hydrogen?
Reply 2
Sunnydazzleeyes
Hi all

I am getting confused with oxidation states of my compounds can someone help me with the oxidation states of the cobalt metal.

[Co(NH3)5Cl]CL2

[Co(NH3)4Cl2)]CL

[Co(acac)2]

[Co(NH3)CO3]NO3-

Also the overall charge of the complex.
Thank you


Work out the overall charge of the complex by comparing with the charge on the counter ions.

For example, in [Co(NH3)5Cl]CL2, we know that Cl has a -1 charge, and there are two of them, so to make the compound neutral the charge on the complex part must be 2+.

Now, to work out the oxidation state of the cobalt you need to think about the charge on each of the ligands and also the overall charge of the complex.

So we know the complex is [Co(NH3)5Cl]](2+). We know that NH3 is neutral and Cl is -1. So the contribution to the charge from the ligands is -1 overall. So to get the complex to have an overall +2 charge this means that the cobalt contributes +3, which is its oxidation state.

You can use this expression : metal ox state = Overall complex charge - combined charge contribution from ligands, or just reason it out as above.

FYI, acac and CO are neutral.
ooze
Work out the overall charge of the complex by comparing with the charge on the counter ions.

For example, in [Co(NH3)5Cl]CL2, we know that Cl has a -1 charge, and there are two of them, so to make the compound neutral the charge on the complex part must be 2+.

Now, to work out the oxidation state of the cobalt you need to think about the charge on each of the ligands and also the overall charge of the complex.

So we know the complex is [Co(NH3)5Cl]](2+). We know that NH3 is neutral and Cl is -1. So the contribution to the charge from the ligands is -1 overall. So to get the complex to have an overall +2 charge this means that the cobalt contributes +3, which is its oxidation state.

You can use this expression : metal ox state = Overall complex charge - combined charge contribution from ligands, or just reason it out as above.

FYI, acac and CO are neutral.


For [Co(NH3)5Cl]Cl2
oxidation state Cl = -1, NH3 = 0 therefore Co = 2+

overally charge I got is 2+

for [Co(NH3)4Cl2]Cl

oxidation states Cl = -2 NH3 = 0 therefore Co = 1+

overall charge = ?

for [Co(acac)2]
oxidation state acac= 0 or is it -2 as 2 oxgyens are coordinated to the cobalt, colbalt = 1+ or 3+

for Co(NH3)CO3
Oxidation state NH3 = 0 CO3 = Is it -2 since 2 oxygen is coordinated to the cobalt? Overall charge ??:s-smilie:
Reply 4
Sunnydazzleeyes
For [Co(NH3)5Cl]Cl2
oxidation state Cl = -1, NH3 = 0 therefore Co = 2+

overally charge I got is 2+

for [Co(NH3)4Cl2]Cl

oxidation states Cl = -2 NH3 = 0 therefore Co = 1+

overall charge = ?

for [Co(acac)2]
oxidation state acac= 0 or is it -2 as 2 oxgyens are coordinated to the cobalt, colbalt = 1+ or 3+

for Co(NH3)CO3
Oxidation state NH3 = 0 CO3 = Is it -2 since 2 oxygen is coordinated to the cobalt? Overall charge ??:s-smilie:


You need to work out the overall charge on the complex part first.

In the second question: [Co(NH3)4Cl2]Cl

The complex is [Co(NH3)4Cl2] and the counter ion is Cl. Cl is -1 therefore the overall charge of the complex is +1, ie the formula is [Co(NH3)4Cl2]+.

Using this, then work out the charge on cobalt.

metal ox state = overall complex charge - ligand charge

Co ox state = +1 - (4 x NH3 + 2xCl) = +1 - (-2) = +3.
ooze
You need to work out the overall charge on the complex part first.

In the second question: [Co(NH3)4Cl2]Cl

The complex is [Co(NH3)4Cl2] and the counter ion is Cl. Cl is -1 therefore the overall charge of the complex is +1, ie the formula is [Co(NH3)4Cl2]+.

Using this, then work out the charge on cobalt.

metal ox state = overall complex charge - ligand charge

Co ox state = +1 - (4 x NH3 + 2xCl) = +1 - (-2) = +3.


therefor Co oxidation is +3 and charge is +1 for [Co(NH3)4Cl2]Cl

so for [CO(NH3)5Cl] Co oxidation is =

[Co(NH3)5Cl2]Cl, Cl is -2 and counterion outside the bracket is -1
therefore oxidation of Co + (-2) = -1
Co= (2+1)
Co=+3

charge = +2
is the above correct?

Also what is the overall charge of acac? Is it -2 as two oxgyen is attatched to Co. acac2-?

And the oxidation state of CO3 where 2 oxygen binds to the Co metal. CO3?

thanks for your help :smile:
Reply 7
Sunnydazzleeyes
therefor Co oxidation is +3 and charge is +1 for [Co(NH3)4Cl2]Cl

so for [CO(NH3)5Cl] Co oxidation is =

[Co(NH3)5Cl2]Cl, Cl is -2 and counterion outside the bracket is -1
therefore oxidation of Co + (-2) = -1
Co= (2+1)
Co=+3

charge = +2

I think you confused the formula a bit there ... there are 2 chlorines outside the complex in your question, and only one inside.

If we were to follow this one through though: [Co(NH3)5Cl2]Cl, then the charge on the complex would be +1, because it has to neutralise the -1 Cl on the outside of it.

The ligands would be indeed have a -2 charge, so to get the overall charge to be +1 the cobalt does need to contribute +3.

Sunnydazzleeyes
is the above correct?

Also what is the overall charge of acac? Is it -2 as two oxgyen is attatched to Co. acac2-?

And the oxidation state of CO3 where 2 oxygen binds to the Co metal. CO3?

thanks for your help :smile:


Acac is this, which is a neutral ligand.

Pretty sure that CO3 is supposed to mean 3 lots of a Carbon Monoxide molecule, which is a neutral ligand.

So now try the last two! :yep:
ooze
I think you confused the formula a bit there ... there are 2 chlorines outside the complex in your question, and only one inside.

If we were to follow this one through though: [Co(NH3)5Cl2]Cl, then the charge on the complex would be +1, because it has to neutralise the -1 Cl on the outside of it.

The ligands would be indeed have a -2 charge, so to get the overall charge to be +1 the cobalt does need to contribute +3.



Acac is this, which is a neutral ligand.

Pretty sure that CO3 is supposed to mean 3 lots of a Carbon Monoxide molecule, which is a neutral ligand.

So now try the last two! :yep:


acac is -1 and CO3 is -2!

I worked out [Co(acac)2] charge=0, Co oxidation = +2

[Co(NH3)CO3]NO3
Charge = +1
Oxidation Co = 3+

is that correct? :woo:
Reply 9
Sunnydazzleeyes
acac is -1 and CO3 is -2!

I worked out [Co(acac)2] charge=0, Co oxidation = +2

[Co(NH3)CO3]NO3
Charge = +1
Oxidation Co = 3+

is that correct? :woo:

Ooooh yeah, acac anion is the ligand :o: So yep, charge is 0, ox state is +2 :yep:

And yeah, I didn't realise that was carbonate :o:

Soo, charge is +1, and ox state is +3, yep yep :biggrin:
ooze
Ooooh yeah, acac anion is the ligand :o: So yep, charge is 0, ox state is +2 :yep:

And yeah, I didn't realise that was carbonate :o:

Soo, charge is +1, and ox state is +3, yep yep :biggrin:


Hi its me again, I have a small question to ask

What is the oxidation state of Cr in

[Cr(H2NC2H4NH2)2](SO4)3

When H2NC2H4NH2 is 0 and SO4 is -2
Im just a bit confused as there is two Cr.

thank you
Sunnydazzleeyes
Hi its me again, I have a small question to ask

What is the oxidation state of Cr in

[Cr(H2NC2H4NH2)2](SO4)3

When H2NC2H4NH2 is 0 and SO4 is -2
Im just a bit confused as there is two Cr.

thank you


there isn't two Cr, there is two H2NC2H4NH2's :smile:

3 x (SO4(2-)) = -6 => Cr = +6
EierVonSatan
there isn't two Cr, there is two H2NC2H4NH2's :smile:

3 x (SO4(2-)) = -6 => Cr = +6


My mistake it was suppose to be [Cr(H2NC2H4NH2)]2(SO4)3
Sunnydazzleeyes
My mistake it was suppose to be [Cr(H2NC2H4NH2)]2(SO4)3


ahh okay - well it's just +6/2 = +3 then
EierVonSatan
ahh okay - well it's just +6/2 = +3 then


Thanks

also what is oxidation state of [Cr(H2O)6]3+
as the H2O are neutral does that make the Cr = +3
Sunnydazzleeyes
Thanks

also what is oxidation state of [Cr(H2O)6]3+
as the H2O are neutral does that make the Cr = +3


Indeed it does :biggrin:
Why NH3=0