[INeedSerotonin]

Hello

Could you please help me with this exercise?



It says "the nitrogen from NH4ClO4 suffers oxidation to NO" and asks me to assign "true" or "false". However, I cannot understand how this happens, since the answer is "true". In the first compound, it has an oxidation number of +5; and in the last, it has an oxidation number of +2. So it reduces, right?

Perhaps the exercise was elaborated wrongly?

Thank you

[Borek]

In the first compound, it has an oxidation number of +5; and in the last, it has an oxidation number of +2.

Explain how you got these numbers.

[INeedSerotonin]

In the first compound, it has an oxidation number of +5; and in the last, it has an oxidation number of +2.

Explain how you got these numbers.

I did it like this:

NH₄ClO₄

N + 4 - 1 - 8 = 0
N = 8 + 1 - 4
N = +5

(I replaced H for 4, since there are four H; and Cl for -1; and O for -8, since there are 4, and each is -2)

For NO, I did just N - 2 = 0 .:. N = +2

[Corribus]

Think in terms of complex ions: ammonium and perchlorate. Hint: chlorine is not a -1 charge here.

[INeedSerotonin]

Ohhh, so I can do NH4 = +1, and find N = -3 ?

This is so strange to me. How can chlorine not be -1? Doesn't it need one electron to be complete like a noble gas?

[Borek]

How can chlorine not be -1?

In most compounds - yes, not in oxoacids (nor interhalogen compounds).

Doesn't it need one electron to be complete like a noble gas?

This is more of a rule of thumb than a serious rule.

Think: it doesn't work for elements that have more than one valency. Fe²⁺ & Fe³⁺, S in H₂SO₃ and H₂SO₄ and so on.

[INeedSerotonin]

Thank you very much, guys! I always learn a lot here! 

[AWK]

There were times when the chlorine atom in HClO4 could be assigned a degree of oxidation of -1. At that time it was thought that chlorine could not have any other valence.
August Wilhelm Hofmann, Proceedings of the Royal Institution, 4, 401-430 (1865)
http://chem125-oyc.webspace.yale.edu/125/history99/6Stereochemistry/models/H4hcl.JPG

[Corribus]

Apparently they also thought all the oxygen atoms were in a chain. What a bunch of dummies! /jk

[MNIO]

on the left...
  NH4ClO4 is ammounium perchlorate.. a salt of perchloric acid  HClO4
  ClO4- ion has a -1 charge.. .ClO4-. 
  So the NH4 has a +1 charge.
  Each H has a +1 charge (because the N has the higher electronegativity 3.04 vs 2.20)
  so the N is -3. get that?
      1 * N + 4 * (+1) = +3 -----> N = -3

on the right..
  N in NO is +2.. why?  O is -2.  the overall NO has zero charge (no charge is shown so it's zero)

by definition
  reduction = reduction in charge (or oxidation state)
  oxidation = increase in charge

so the N is oxidized.