EXPLOSIVE CHEMISTRY
O2N
H
C
H
C
C
C
C
O2N
C
NO2
H2C
O NO2
H2C
O NO2
H2C
O NO2
C
N
C
N
O2N
C
NITROGLYCERIN
H2
N
H2
CH3
TNT
NO2
H2
NO2
RDX
As you saw in the movie “Ka-Boom!”, putting nitro groups (-NO2) on a hydrocarbon is a
good way to store a lot of chemical potential energy in a molecule. In this exercise you’ll
apply some of the chemistry we’ve been using this quarter to three high explosives that
contain nitro groups: TNT (short for trinitrotoluene), nitroglycerin, and RDX (short for
cyclotrimethylenetrinitraime).
1. Use the structural formulas given above to write molecular formulas for each
explosive. Then determine the molar mass and % nitro for each explosive.
2. For each reaction write a balanced chemical equation with state symbols.
a. Solid TNT combines with oxygen gas to form carbon dioxide gas,
nitrogen gas, and water vapor.
b. Liquid nitroglycerin decomposes into carbon dioxide, nitrogen, and water
vapor (all gases).
c. RDX decomposes into carbon monoxide, water vapor, and nitrogen gas.
3. Explosives get their shattering power by rapidly producing large volumes of gas
for a given volume of explosive.
a. How many moles of gas are produced for one mole of TNT? of
nitroglycerin? of RDX?
b. Mole for mole, gases take up about 800x the volume of liquids or solids, at
room temperature. Producing gases at high temperatures expands them 8x
more than the space they’d occupy at room temperature. For every cc of
TNT how many cc of gas are produced? for nitroglycerin? for RDX?
4. The heat of combustion of TNT is 820.7 kcal/gram, and for nitroglycerin its 368.4
kcal/gram.
a. Convert these values from kcal/gram to kcal/mole.
b. How do these values compare to the heat of sugar, which is 669
kcal/mole?
ANSWERS
1. TNT = C7H5N3O6; molar mass = 227.1 g; %NO2 = 60.8%
nitro = C3H6N3O9; molar mass = 228.1 g; %NO2 = 60.5%
RDX = C3N3H6N3O6; molar mass = 222.1 g; %NO2 = 62.1%
2. (TNT) 4 C7H5N3O6 (s) + 21O2 (g)  28 CO2 (g) + 10H2O (g) + 6N2 (g)
(nitro) 2 C3H6N3O9 (l)  6CO2 (g) + 3N2 (g) + 6H2O (g)
(RDX) C3N3H6N3O6 (s)  3CO (g) + 3H2O (g) + 3N2 (g)
3. (a) 4 moles TNT  28+10+6 = 44 moles gas; 44/4 = 11 moles gas per
mole of explosive
4 mole Nitro  6+3+6 = 15 moles gas; 15/2 = 7.5 moles gas per mole of
explosive
1 mole RDX  3+3+3 = 9 moles gas per mole of explosive
4. (b) 800x for gas AND 8x for volume = 6400x expansion per mole
TNT = 6400 x (11 moles gas/1 mole explosive)= 70,400cc gas per cc TNT
nitro = 6400 x (7.5 mol. gas/1 mol. explosive) = 48,000 cc gas per cc nitro
RDX: 6400 x (9 mol. gas/1 mol. explosive) = 57,600 cc gas per cc of RDX
5. (a) 820.7 kcal/1 g TNT * (227.1 g/mole) = 186,300 kcal/mole
368.4 kcal/g nitro * (228.1 g/1 mole) = 84,030 kcal/mole
5. (b) TNT releases 186,300 kcal /669 kcal = 278x more energy per molecule than
glucose; nitroglycerin releases 84,030 kcal/669 kcal = 126x more energy per
molecule than glucose