Explosives - Explosive Power

Question 1

What is the oxygen balance equation?

Answer 1

• Equation is: d - (2a) - (b/2)
  
  • d = amount of oxygen available
  • a = number of carbons
  • b = number of hydrogens

Question 2

How is the oxygen balance calculated for any molecule with the formula C_aH_bN_cO_d?

Answer 2

The oxygen balance of any explosive of general formula C_aH_bN_cO_d with a molecular weight M can be calculated as shown in the picture.

If the oxygen balance is less than zero the carbon and hydrogen cannot be fully oxidised.

Question 3

What are the K-W rules?

Answer 3

1. C atoms to CO
2. H atoms to H₂O
3. CO to CO₂
4. N to N₂

Question 4

What is the equation for the heat of detonation?

Answer 4

• Once we know the detonation products we can calculate the enthalpy of detonation.
• Enthalpy change = (sum of enthalpy of products) - (sum of enthalpy of reactants)
• Enthalpy of reaction (Q) = (enthalpy change / Molecular mass) x 1000

Question 5

How is the volume of detonation calculated?

Answer 5

C₄H₈N₈O₈ → 4CO + 4H₂O + 4N₂

• 12 moles of gas are produced from 1 mole of HMX.
• Volume of gas, V = 12 x 22.4 L mol^-1 = 268.8 Lmol^-1

Or per kg of HMX:

V = 268.8 x (1000/296) = 908.1 L kg^-1

Question 6

How is explosive power calculated from the enthalpy of reaction and volume of detonation?

Answer 6

Explosive power = Q x V

Explosive power (HMX) = 5010 kJ kg^-1 x 908.1 L kg^-1

= 4.550 x 10⁶ kJ L kg^-2