The compound hexaazaisowurtzitane is the highest-energy...

The compound hexaazaisowurtzitane is the highest-energy explosive known ( $C$ \& $E$ News, Jan. 17,1994, p. 26 ). The compound, also known as CL-20, was first synthesized in 1987 . The method of synthesis and detailed performance data are still classified because of CL-20's potential military application in rocket boosters and in warheads of "smart" weapons. The structure of CL-20 is In such shorthand structures, each point where lines meet represents a carbon atom. In addition, the hydrogens attached to the carbon atoms are omitted; each of the six carbon atoms has one hydrogen atom attached. Finally, assume that the two $\mathrm{O}$ atoms in the $\mathrm{NO}_{2}$ groups are attached to $\mathrm{N}$ with one single bond and one double bond. Three possible reactions for the explosive decomposition of CL-20 are i. $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{~N}_{12} \mathrm{O}_{12}(s) \rightarrow 6 \mathrm{CO}(g)+6 \mathrm{~N}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)+\frac{3}{2} \mathrm{O}_{2}(g)$ ii. $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{~N}_{12} \mathrm{O}_{12}(s) \rightarrow 3 \mathrm{CO}(\mathrm{g})+3 \mathrm{CO}_{2}(g)+6 \mathrm{~N}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)$ iii. $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{~N}_{12} \mathrm{O}_{12}(s) \rightarrow 6 \mathrm{CO}_{2}(g)+6 \mathrm{~N}_{2}(g)+3 \mathrm{H}_{2}(g)$ a. Use bond energies to estimate $\Delta H$ for these three reactions. b. Which of the above reactions releases the largest amount of energy per kilogram of CL-20?

The compound hexaazaisowurtzitane is the highest-energy explosive known ( $C$ \& $E$ News, Jan. 17,1994, p. 26 ). The compound, also known as CL-20, was first synthesized in 1987 . The method of synthesis and detailed performance data are still classified because of CL-20's potential military application in rocket boosters and in warheads of "smart" weapons. The structure of CL-20 is
In such shorthand structures, each point where lines meet represents a carbon atom. In addition, the hydrogens attached to the carbon atoms are omitted; each of the six carbon atoms has one hydrogen atom attached. Finally, assume that the two $\mathrm{O}$ atoms in the $\mathrm{NO}_{2}$ groups are attached to $\mathrm{N}$ with one single bond and one double bond.

Three possible reactions for the explosive decomposition of CL-20 are
i. $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{~N}_{12} \mathrm{O}_{12}(s) \rightarrow 6 \mathrm{CO}(g)+6 \mathrm{~N}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)+\frac{3}{2} \mathrm{O}_{2}(g)$
ii. $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{~N}_{12} \mathrm{O}_{12}(s) \rightarrow 3 \mathrm{CO}(\mathrm{g})+3 \mathrm{CO}_{2}(g)+6 \mathrm{~N}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)$
iii. $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{~N}_{12} \mathrm{O}_{12}(s) \rightarrow 6 \mathrm{CO}_{2}(g)+6 \mathrm{~N}_{2}(g)+3 \mathrm{H}_{2}(g)$
a. Use bond energies to estimate $\Delta H$ for these three reactions.
b. Which of the above reactions releases the largest amount of energy per kilogram of CL-20?

Key Concepts

Bond Energy

Bond energy is the amount of energy required to break a chemical bond between two atoms. In thermochemical assessments, bond energies are used to estimate the energy changes during a chemical reaction by comparing the total energy required to break bonds in the reactants with the total energy released upon forming bonds in the products.

Enthalpy Change (?H) Estimation

Enthalpy change (?H) estimation in chemical reactions involves calculating the difference between the energy needed to break all bonds in the reactants and the energy released when new bonds are formed in the products. This approach provides an approximate measure of whether a reaction is exothermic or endothermic.

Thermochemical Calculations

Thermochemical calculations apply principles from thermodynamics, such as the conservation of energy, to determine the heat absorbed or released in chemical reactions. These calculations frequently utilize bond energies, reaction stoichiometry, and Hess’s Law to compute the overall enthalpy change of a reaction.

Explosive Decomposition

Explosive decomposition refers to the rapid breakdown of a compound into gaseous products, releasing a large amount of energy quickly. This process is characterized by a high energy density and involves the conversion of reactant bonds into products with relatively lower bond energy, thereby resulting in a significant release of heat and gas expansion.

Energy per Unit Mass (Energy Density)

Energy per unit mass, or energy density, is a measure of the energy released relative to the mass of the reacting substance. In reactions involving energetic materials, comparing the energy released per kilogram allows for assessing the efficiency and potential application of the explosive in various military and industrial contexts.

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