Last week, millions of TV viewers nationwide watched for about 17 hours one of the most stunning live TV transmissions in Indonesian television’s history about operation of capturing terrorists. The terrorist who defended inside the shack was believed to be Indonesia’s most wanted earthling: Noordin M. Top. When the operation was up, the thought of Top being killed was in the air. But soon through the later DNA identification revealed that the dead terrorist was not Top. Of course it should not play down the efforts of the police to foil terrorism because whatever the result ended in we have to keep encouraging the force to thwart terrorism and I believe most of Indonesians still have one voice in unison that the top-rank terrorist Top must be captured dead or better alive.
Through this article I will not take you to discuss the action-packed (is it?) operation, in that I’m not interested. Instead I’m gonna bring you to see how a chemical reaction occurs in explosion. While making a bomb requires a trained person and a dab hand at it (which definitely I am not), to understand the chemical reaction in explosion does not call for rocket scientists! Ok without anymore beating about the bush, let’s find out the lowdown on the chemical reaction in explosion.
Explosions occur when a chemical reaction takes place rapidly and with a considerable increase in volume. They often involve compounds rich in nitrogen such as nitroglycerine, trinitrotoluene (TNT) and ammonium nitrate (Yes! You are right! Ammonium nitrate is a common fertilizer!) These compounds can decompose readily, yielding nitrogen gas as one of the products. Explosive mixtures are used for a wide variety of projects ranging from earthmoving, building demolition to making bombs. Vehicles loaded with ammonium nitrate, vests stuffed with the explosives to be worn by suicide bombers or luggage loaded with the explosives (the two last options are more common in Indonesia) have been used in terrorist attacks worldwide. The compound, ammonium nitrate, mixed with fuel oil and it is dubbed ANFO (ammonium nitrate-fuel oil) is an explosive with enormous destructive power.
The chemical reaction taking place in explosion are usually the result of redox (reduction-oxidation) reactions. The ammonium nitrate is both reduced and oxidised with ammonium ion acts as the reducing agent whereas nitrate ion acts as the oxidising agent. (Recall your high school chemistry class! ) The fuel oil provides additional oxidisable material. Now let’s take a look how the chemical reaction occurs in a simple chemical reaction. The fuel oil is usually a long carbon chained alkane or cycloalkane:
52 NH4NO3 (s) + C17H36 (l) ————-> 52 N2 (g) + 17 CO2 (g) + 122 H20 (g)
The reaction starts with 53 mol of materials, most of it solid and liquid, in the end it yields 191 mol of products, all gases! A reaction of solid and/or liquid reactants that generates gaseous products involves a huge volume increase. This enormous volume increase that yields the explosion with flash and very loud boom which are characteristic of the explosion. The volume increase also gives rise to a shockwave travelling at an enormous speed of up to 9000 metres per second with monstrous pressure of up to 700,000 atmospheres.
So why ammonium nitrate?? It is because a common fertilizer, and fuel oil is also common and it is not hard to find one. The fact that both these materials are so accessible to potential terrorists is cause for serious concern. The compound that nourishes plants and cash crops can massively kill people and devastate physical structures in the face of terrorism!