Question

assign oxidation numbers to each element in the compounds below: Fe2O3(s)
CO(g)
Fe(s)
CO2(g)
O2(g)

Answer 1

This still confuses me..

Answer 2

I think Fe is +3 and O is -2 but not too sure..

Answer 3

+3 *2 for Fe and -2 * 3
Now, we want it all equals to zero when we add them up
(+3( 2) )+ (-2 (3) = 0
6-6=0

Answer 4

+3 *2 for Fe and -2 * 3 for O ********* forgot oxygen :p

Answer 5

in this compound Fe2O3(s) Fe is +3 and O -2
but in Fe(s) the oxidation state is 0

Answer 6

it's a compound

Answer 7

okay now i'm confused

Answer 8

the same element can have different oxidation's states depending on the compound or if they are in the elemental state. There are a series of rules to assign the oxidation state . are you familiar with the rules?
http://chemistry.about.com/od/generalchemistry/a/oxidationno.htm

Answer 9

i've been reading over them but not off the top of my head

Answer 10

You were right, @kmh1001 the ON of Fe is +3 and O is -2

Answer 11

in the first case you have to look at the O and assign a -2 oxidation number, as @Zale101 explain you earlier, then the Fe is going to be a +3 to keep all the charge of the compound equal to 0.

Answer 12

okay so what about CO becuase that one throws me for a loop.

Answer 13

CO(g)

Answer 14

you stat again with the O with a -2, then the C has to be +2 to keep the compound total charge equal to 0

Answer 15

Oh, when you said Fe, i thought u were talking about Fe2O3, that's why i said it's a compound lol my bad @Cuanchi

Answer 16

Ohhhh okay makes sense

Answer 17

The Fe(s) it is at elemental form and according to the rule #2 the oxidation state is 0

Answer 18

Okay i get it now

Answer 19

thank you

Answer 20

The CO2(g) it is a compound, so you start from the O with a -2, but in this case you have 2 oxygen, so you will have to multiply by 2 = (-4) so now the C a difference than in the CO here has a oxidation state of +4 to keep the balance of charges equal to 0. (the rule #9)

Answer 21

awesome, makes total sense now. Thank you so much!