What happens chemically when dynamite explodes (include reactions/coefficients/etc)?

Question

I tried looking for it and cant find it could you do the same with TNT.

Answer 1

Dear Alena,

Nitroglycerin is considered to explode as:

4 C₃H₅N₃O₉ --> 12 CO₂ + 10 H₂O + 6 N₂+O₂

It does so nicely -- just drip some from a syringe onto the floor, and it explodes with little pops (note: you would only use a microsyringe, such as a 10 μL one, to gently do this -- it's far too hazardous to manipulate larger quantities of neat GTN by hand).

 

Note to Jon P. -- usually kieselguhr is the support for dynamite, not sawdust.

 

But there's considerable variation in the stated explosion reaction stoichiometry for trinitrotoluene, ranging from 

2 C₇H₅N₃O₆ → 3 N₂ + 5 H₂O + 7 CO + 7 C

to 

2 C₇H₅N₃O₆ → 3 N₂ + 5 H₂ + 12 CO + 2 C

As you can see, some of the oxygens may be "stolen" from the water by the carbons. This represents the "water gas shift reaction", an extremely important industrial reaction. In any event, there are some extra elemental carbons produced -- the explosion is "sooty".

So, why the difference? It's because of the great abundance of O's in nitroglycerin, and the relative scarcity of them, in TNT.

By the way, you shouldn't generally expect combustion reactions to generate uncertain distributions of products! However, many reactions used to synthesize desired chemicals generate a mix of products. It's up to chemists to figure out how to minimize the formation of such byproducts, and remove them from the desired product material if they occur at unacceptable levels (in a drug substance for human or veterinary use, for example).

You might want to also look up the difference between "decomposition", "explosion", and "detonation"!