Re: Why is hydrogen so explosive, and what caused the Hindenburg to explode?

That question was interesting, I learned a lot!

1.) Why is hydrogen so explosive?
You have different kinds of chemical reactions, you have reactions where energy will be set free ("exothermic") and reactions in which energy is needed ("endothermic"). The first kind is for example burning wood (or hydrogen ...), the second one is cleaving water into its elements (i.e., oxygen and hydrogen) by electric power. The kind of reaction depends whether the reactants or products of the reaction have more energy.

If you burn hydrogen, it reacts with oxygen in the air and forms water. The energy of water is much lower than the energy of hydrogen and oxygen; this means that, if you initiate the reaction (!!! important !!!) it will not stop until all the hydrogen has reacted with oxygen (of which you have more than enough in the atmosphere). So a lot of energy will be set free and it is "explosive" (in the Hindenburg case it actually just burned, it took quite a long time until all the hydrogen was burned - not minutes, but many seconds).


2.) What was the cause of the accident?
I read on a few web-pages - actually no one knows the answer for sure! One version is that the people on board wanted to land and were throwing ropes to the ground. Because there was a potential difference between the Hindenburg and the ground (a kind of a "battery", but one pole "on board" and the other on the ground) there was a small static discharge ("lightning") when the rope hit the ground. Then the surface of the Hindenburg started to burn, and ignited the hydrogen inside.

Actually the Hindenburg was built to use helium (non-inflammable), so most safety features for hydrogen were not built in; that made it "easier" for the disaster to happen. The paint on the surface of the dirigible was quite inflammable, otherwise it probably wouldn't have happended. (Check out http://www.e-sources.com/hydrogen/safety.html)
But acutally no one knows!

Andreas