Strike day, and a bit of free time to play around with some home made explosives.
Nitrogen triiodide is worryingly easy to make, and extremely unstable. It is a contact explosive when dry, and produces a beautiful plume of iodine vapour mixed with nitrogen gas when detonated.
As you can see and hear from the video, the explosion is fairly impressive given the small quantity used. You can see that the metre ruler suffers for its art, and you may just be able to make out Mr Chivers' exclamation from his nearby office just as it goes off.
Anyone interested in why it's so unstable will need to consider the entropy change for the reaction.
2 NI3 (s) → N2 (g) + 3 I2 (g)
The large increase in the number of moles from left to right, in addition to the production of gases from a solid, leads to an enormous increase in entropy. Also, the reaction is clearly exothermic. These two factors are ideal for giving a negative free energy change for the reaction, indicating a highly likely, spontaneous reaction.
