[beLIEveR]

I've been asked to write about how oxidation reactions are used to cause explosions, giving examples of both high and low explosives.

So far I've worked out the oxidation states in the reaction of gunpowder, and believe that the change in oxidation state of nitrogen from +5 (in KNO₃) to 0 (in N₂) is something to do with it.

The high explosive that I'm supposed to give an example of is nitroglycerine (C₃H₅N₃O₉). The oxidation states of carbon dioxide, water, nitrogen and oxygen are simple enough, but I'm stuck on nitroglycerine. I'm assuming each O would have a state of -2, and each H a state of +1, but haven't got a clue about N or C atoms.

Am I going in completely the wrong direction here, or am I just missing something fairly simple?

[Mitch]

draw the structure.

[beLIEveR]

Structure:

H₂C-O-NO₂
    |
..HC-O-NO₂
    |
H₂C-O-NO₂

I know all of the oxygens will have an oxidation state of -2.
On top of that, I'm fairly suer the hydrogens are meant to be +1. I think the Ns will either be +3 or +5, having looked through my textbook. But still not very sure.

[Mitch]

hydrogen will be -1.

[beLIEveR]

Meaning... as NO₃ has an overall charge of -1, N will be +5 and C +3. Thanks.

The thing is, because I thought hydrogen was almost always +1 I was completely thrown. As a general rule, how do you know whether hydrogen has an oxidation state of +1 or -1?

[Mitch]

I suppose, acidity.

[Grumples]

I don't know if you can come up with a general rule regarding whether H is +1 or -1.  As  I learned redox, you can only be sure about O being -2, and sometimes (such as in H2O2) even that isn't right.  You just have to look at the structure and think about what configurations would work.

[AWK]

First of all, the oxidation number (ON) is a quite conventional matter, but usually chemists use some rules, a periodic table and electronegativity as an assistance. Only these rules fullfills a superior role:
1. oxidation number for elements
2. sum od oxidation states
and
general rule for any reaction - the same number of atoms and charges on both sides of reaction.

Whether a hydrogen shows oxidation number +1 or -1, we decide using our chemical knowledge and electronegativity, eg
CH4 - ON for H is +1
Why not +2 - because hydrogen cannot loose 2 electrons ( but using above rules for ON of H =+2 you still can balance a redox reaction)
SiH4 - ON for H is -1
Why not -2 - because hydrogen can easy gain only 1 electron ( but ON = +1  for H and ON = -4 for Si also will work during balancing  because rule 2 is fulfilled.

Note - putting ON = 0 for all atoms in elements and compounds, the rules 1 and 2 are fulfilled, and the last rule still allows us to balance any reaction (computer programs usually work in this way)