Question

Identify the oxidation numbers of the following
A. Sulfur as a reactant and product in S8+12 O2 --> 8 SO3
B. Nitrogen in the following compounds or ions N2O5 NO3 NO2 Ca3N2

Answer 1

We need to figure out some charges.

Answer 2

Can you tell me what the charge of each S in S8 is?

Answer 3

im am not sure. \[S _{8}\]

Answer 4

\[S _{8}+12O _{2}-->8SO _{3}\]

Answer 5

Ok. Nonmetal bonded to nonmetal is a covalent bond which means electrons are shared, not transferred. So each S has an oxidation number of 0.

Answer 6

Oxygen almost always has an oxidation number of -2 in compounds.

Answer 7

And the oxidation numbers of neutral compounds must sum to 0.

Answer 8

So, since we have 3 oxygens in SO3, the oxidation number from all three oxygens is -6. To sum to 0, the S needs to be +6.

Answer 9

Make sense?

Answer 10

yes. but what about the 12\[O _{2}\]

Answer 11

12O2

Answer 12

Uncombined elements have oxidation number of 0, but the question only asked for the oxidation numbers of S.

Answer 13

oh makes sense

Answer 14

:) Can you try N2O5?

Answer 15

would N be -5

Answer 16

5

Answer 17

Remember that O is virtually always -2.

Answer 18

10

Answer 19

you said because of that oxygen would be -10 and the sum would need to be 0 so Nitrogen needs to be 10

Answer 20

But there are 2 N.

Answer 21

So each one needs to be 5.

Answer 22

I understand why N needs 5 but why does O need 5?

Answer 23

I'm not sure what you mean.

Answer 24

you said each one needs 5 I do understand why nitrogen needs 5 to off set oxygens -10 right?

Answer 25

The oxidation number of N needs to be 5 (total of 10) to balance the oxidation number of O (total of -10).

Answer 26

ok got it.
NO3
nitrogen needs 6 right?

Answer 27

Perfect. :)

Answer 28

NO2?

Answer 29

4

Answer 30

Great!

Answer 31

the last one I am stumped

Answer 32

to take a guess 3

Answer 33

Good guess. Remember how I said that oxygen is almost always is -2. Well, group 2 metals are always +2.

Answer 34

The rules are summed up on this website. http://www.chemguide.co.uk/inorganic/redox/oxidnstates.html

Answer 35

-3 then if that is the case

Answer 36

Exactly.

Answer 37

You probably have the rules somewhere in your textbook too.

Answer 38

light bulb. I am starting to understand this chemistry stuff with only 4 weeks left in the semester. awesome.

Answer 39

Nice. Well, better late than never. :)

Answer 40

I have the textbook right next to me and honestly it is like reading a foreign language at times.

Answer 41

Yeah, I know what you mean. Some are better than others.