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Nitrogen Triiodide

The True Value of Nitrogen Triiodide from devin on Vimeo.

Chemistry Background Information
Have you ever seen something detenated by the touch of a feather? Solid Nitrogen Triiodide is an extremely sensitive explosive that is made when Iodine atoms displace the hydrogen atoms in ammonia. The following equation is represented below:
3I2(S) + 2NH3(AQ) = NI3(S) + 3H2(G)
ammonia and Iodine react to form solid Nitrogen Triiodide, NI3(s). Although Nitrogen Triiodide is extremely unstable when dry, detenating from the slightest touch of a feather or even a fly, it is rather stable when dampened. When dry Nitrogen Triiodide explodes it is really decomposing to form more stable products with the following spontaneous reaction:

8NI3NH3(S) → 5N2 + 6NH4I + 9I2

Nitrogen Iodide is instable because it is a product from an unspontaneous endothermic reaction and the products from its decomposition reaction are exothermic and spontaneous causing the system to have a very strong tendency to shift to the decomposed products of Nitrogen Iodide. the following equations represent the endothermic and exothermic reactions:

Exothermic: 2 NI3 (s) external image arrow.gif N2 (g) + 3 I2 (s)
Endothermic: N2 (g) + 3 I2 (s) external image arrow.gif 2 NI3 (s)

The purple vapor that the reaction causes is iodine vapor created from the explosion. Nitrogen triiodide is formed when iodine atoms displace the hydrogen atoms in ammonia NH3 + I = NI3.


The light blue is the nitrogen and the three purples represent the iodide. Together they make the structure of the nitrogen triiodide molecule.

The reason that nitrogen triiodide is so unstable is in part to the structure of the molecules that make up the compound. The iodine atoms are considerably larger than the nitrogen atom that holds them all together. This forces the iodine atoms closer together and puts stress on the bonds. This stress makes the molecule easy to break apart, requiring little energy to set off the explosion.

The reaction is a extremely fast and loud because of the stages that the process goes through. In a split second, nitrogen triiodide goes from a solid to two gasses. The reaction is deafening because of the energy released from the bonds that hold the compound together. The rapid expansion of nitrogen triiodide to nitrogen gas and iodine gas causes the loud blast.

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