Explosions 3

Question 1

What are the Kistiakowsky-Wilson rules and what do they tell you?

Answer 1

Predicts the products of the explosion
1. C atoms to form CO
2. H atoms to form H2O
3. CO molecules to form CO2
4. N atoms to form N2

Question 2

What is the equations for the number of oxygen atoms required?

Answer 2

CaHbNcOd
OB = d - 2a - b/2

Question 3

What is the equation for oxygen balance?

Answer 3

Ω = (([d-2a-b/2]x16)/M) x 100
where M is the molecular weight

Question 4

When are the Kistiakowsky-Wilson rules applied?

Answer 4

When the oxygen balance is negative (>-40%)

Question 5

For HMX: C4H8N8O8 (Ω > -40%) what are the products produced?

Answer 5

C4H8N8O8 (s) –> 4CO (g) + 4H2O (g) + 4N2 (g)

Question 6

Which gaseous product would qualitativley indicate near-neutral or positive oxygen balance?
a. CO2
b. CO
c. H2O
d. N2
e. H2

Answer 6

CO2
* Last step in our KW rules so will only form this if we have oxygen left over

Question 7

What is the enthalpy (heat) of detonation calculation?

Answer 7

Δd𝐻 = ∑𝜈𝑝𝑟𝑜𝑑Δf𝐻𝑝𝑟𝑜𝑑 −∑𝜈𝑟𝑒𝑎𝑐𝑡 Δf𝐻𝑟𝑒𝑎𝑐𝑡
* Total enthalpy of formation for the products - total enthalpy of the reactants

Question 8

Enthalpy (heat) of detonation is often expressed as heat per kg, how would you convert this from kj mol-1?

Answer 8

Multiply by 1000/molecular weight

Question 9

Calculate the enthalpy of detonation for HMX.
C4H8N8O8 –> 4CO + 4H2O + 4N2
C4H8N8O8 = +75
CO = -110
H2O = -242
N2 = 0

Answer 9

Δd 𝐻 = [-1408] - [75] = -1483 kj mol-1
-1483 x (1000/296) = -5010.1 kj kg-1

Question 10

What does the volume of detonation depend on and what is the equation?

Answer 10

Moles of gas released
V = moles x volume of one mole of gas
Volume of one mole of gas = 22.4 L mol-1

Question 11

What is the volume of detonation for HMX?
C4H8N8O8 –> 4CO + 4H2O + 4N2

Answer 11

1 mole of HMX gives 12 moles of gas
V = 12 x 22.4 L mol-1 = 268.8 L mol-1
Express as L kg-1 = 268.8 x (1000/296)

Question 12

What is explosive power the measure of?

Answer 12

Enthalpic and entropic components of an explosion

Question 13

What is the equation for the explosive power?

Answer 13

Explosive power = heat x volume of gas

Question 14

When do you use the modified Kistiakowsky-Wilson rules?

Answer 14

Whent he oxygen balance is more negative than -40%

Question 15

What are the modified Kistiakowsky-Wilson rules?

Answer 15

1. H atoms to form H2O
2. C atoms to form CO
3. If C atoms remaining (and no O) for solid C
4. N atoms to form N2

Question 16

Calculate the oxygen balance of TNT?
C7H5N3O6 (molecular weight 227)

Answer 16

Ω = ([6-(2x7)-(5/2)]x16)/227 x 100 = -74.0%

Question 17

Apply the modified K-W rules to TNT (oxygen balance = -74%)
C7H5N3O6

Answer 17

C7H5N3O6 (s) –> 7/2 CO (g) + 7/2 C (s) + 5/2 H2O (g) + 3/2 N2 (g)