fertilizers. Ammonia (NH 3 ) consists of nitrogen, essential for plant growth.
Ammonia & Ammonium ions (NH 4 + ) are converted into nitrates by soil bacteria, which are then absorbed by the plants for nitrogen.
Examples: Anhydrous Ammonia, Ammonium Nitrate and Ammonium Sulphate
Weak ammonia solutions are also widely used as commercial and household cleaners and detergents.
Modern Ammonia Production (The Haber Process) Achieved by the direct combination of hydrogen and nitrogen, over an iron or aluminium catalyst. Hydrogen is obtained from the decomposition of methane by heating. Nitrogen is obtained from the distillation of liquefied air. The reaction is shown below: N 2 (g) + 3H 2 (g) ⇌ 2NH 3 (g)
Fertilizer (Ammonium Nitrate)
Ammonia is a thermally unstable compound.
It has a melting point of 169ºC.
Ammonia can result in an endothermic reaction or an exothermic reaction, depending on
environmental factors such as the pH, confinement and temperature.
Since Ammonium nitrate is a thermally unstable compound, it produces a large amount of heat
during exothermic decomposition.
During decomposition, it also produces a large volume of oxygen gas for combustion of other fuels.
Fertilizer (Ammonia Nitrate)
When carried out in a closed system under low temperature,
Endothermic dissociation of NH 4 NO 3 into NH 3 and HNO 3 takes place [a reversible reaction].
Ammonia is not allowed to escape the system
There is no change in the pH of the environment and the amount of ammonia in the system.
Endothermic dissociation of NH 4 NO 3 into NH 3 and HNO 3
takes place initially.
However, ammonia escapes the system when produced.
A decrease in the pH of the environment and increase in temperature enhances the exothermic decomposition of NH 4 NO 3 (below)
Since a large net amount of heat is released during the decomposition, ammonium nitrate can be used as an
Fertilizer (Explosive) NH4NO3 NH 3 + HNO 3 [ΔH > 0] 2NH 4 NO 3 2N 2 + 4H 2 O + O 2 [ΔH = -1460 kJ/kg]
During the exothermic decomposition of NH 4 NO 3 ,
the NO 3 - ions oxidize the NH 4 + ions in N 2 O
N 2 O,decomposes into N 2 and O 2 under high temperature, producing a large amount of gas.
A large amount of the oxygen gas produced is used for the combustion of other fuels mixed with the fertilizer
This causes the fuels to combust at a faster rate and produce more heat for the exothermic decomposition
of NH 4 NO 3.
Fertilizer (Explosive) 2NH 4 NO 3 -> 2N 2 + 4H 2 O + O 2 [ΔH = -1460 kJ/kg]
Closed System / Low Temperature Exothermic Fuel Combustion Open System / High Temperature NH 3 leaves system N 2 O + H 2 O Combusting Fuel Combusting Fuel Exothermic N 2 + O 2 + H 2 O Exothermic More oxygen available for combustion of fuel Higher Temperature Higher rate of exothermic decomposition of NH4NO3 EXPLOSION Endothermic NH 4 NO 3 NH 3 + HNO 3 N 2 + O 2 + H 2 O
Why would terrorists use
Fertilizers (Ammonium Nitrate)
are explosive materials
Easily available and obtainable
Not easily detectable
(can pass through metal detectors undetected)
Soluble in water
(easy to avoid detection)
A Terrorist’s Arsenal
For something intended as a gift of life to be used for destructive purposes is truly a tragedy. The End