[al220007]

I was calculating some oxidation states but I couldn't solve 3 of the compounds my teacher gave:

• Cr(ClO₃)₃
• ZnSO₄
• Al₂(SO₄)₃

I know O has oxidation state equals -2 in all of them and Cl on the first compound hasn't oxidation state equals -1 because it's bonded with an O but now I'm stuck.

How should I solve them? Is there any rule I'm missing?

Thanks in advance! 

[Borek]

Would writing these compound dissociated to ions help?

[Orcio_87]

I know O has oxidation state equals -2 in all of them and Cl on the first compound hasn't oxidation state equals -1 because it's bonded with an O but now I'm stuck.

In neutral compound (not cation or anion) sum of the all oxidations states is equal 0.

Cr(ClO₃)₃ is a salt, it dissociate to cation and anion.

[al220007]

Would writing these compound dissociated to ions help?

I hope I did it right:

• Cr(ClO₃)₃ --> Cr³⁺ + 3ClO₃^-
• ZnSO₄ --> Zn²⁺ + SO₄^2-
• Al₂(SO₄)₃ --> 2Al³⁺ + 3SO₄^2-

Now I calculated the oxidation state of each one separatedly and I think the result it's correct!

Example with Cr(ClO₃)₃

3 + 3(5 + 3(-2)) = 0	|	+3 = 3	|	+5 - 2 = -1
Cr(ClO3)3	|	Cr3+	|	3ClO3-

I just need to review the ions charges.

Thank you <3

[Hunter2]

Looks OK.