Chemical Forums

Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: GreenAssailant on October 18, 2011, 11:10:30 PM

Title: Assigning Oxidation No's: Multiple Remaining Atoms Unassigned
Post by: GreenAssailant on October 18, 2011, 11:10:30 PM: 2 Li + 3 Fe(C2H3O2)2 -- > 2 LiC2H3O2 + Fe

Say I want to assign the oxidation states for 3 Fe(C2H3O2)2
First Hydrogen: +1
Then Oxygen: -2

Fe and C are the problem. I am not sure how I know what oxidation no's to assign them. Help?
Title: Re: Assigning Oxidation No's: Multiple Remaining Atoms Unassigned
Post by: AWK on October 19, 2011, 02:11:48 AM: Fe(C₂H₃O₂)₂ is produced from C₂H₄O₂ (acetic acid). Can you assign ocidation number for carbon in this compound?
Moreover, you can see LiC₂H₃O₂ on the right side. Lithium show always ON +1. Can you assign ON for carbon in this compound?
Title: Re: Assigning Oxidation No's: Multiple Remaining Atoms Unassigned
Post by: Borek on October 19, 2011, 04:56:48 AM: To add to what AWK wrote: Fe(C₂H₃O₂)₂ is the iron acetate. Do you know what is a charge of the acetate ion? If so, what must be the charge on the iron? How is the charge of the cation related to its oxidation number?
Title: Re: Assigning Oxidation No's: Multiple Remaining Atoms Unassigned
Post by: GreenAssailant on October 19, 2011, 10:35:16 PM: Quote from: Borek on October 19, 2011, 04:56:48 AM
To add to what AWK wrote: Fe(C₂H₃O₂)₂ is the iron acetate. Do you know what is a charge of the acetate ion? If so, what must be the charge on the iron? How is the charge of the cation related to its oxidation number?

I thought charges would only apply if, for instance, it was a polyatomic ion alone.
I am not sure how this would work. Do we split them up into their ion forms and assign the oxidation numbers?
Title: Re: Assigning Oxidation No's: Multiple Remaining Atoms Unassigned
Post by: Borek on October 20, 2011, 02:49:15 AM: Molecule on the whole is neutral, so if it is made of several ions, their charges must cancel. We know that acids like HCl or HNO₃ are monoprotic and they dissociate giving anions with a single negative charge - Cl^-, NO₃^-. That means in a salt like FeCl₂ Fe must be +2 - otherwise the molecule would be not neutral. It also means in Cr(NO3)₃ Cr must be +3 for the same reason. That allows a quick calculation of oxidation number for the metal. It doesn't tell us anything about oxidation numbers of N nor O in NO₃^-.