Answer to Question #29376 in Physical Chemistry for Antoinette

Question

a) For each pound (454g) of ammonium nitrate that exploded (products being nitrogen gas, oxygen gas, and water vapor) how many kJ of thermal energy were released and how many L of gas (measured at 1atm and 25degreeC) were formed? We know deltaHf for ammonium nitrate is -87.37 kcal/mol
b) The density of ammonium nitrate is 1.725g/cm^3. How many litres did the volume of the system increase when the pound of ammonium nitrate exploded?

Answer 1

For this process the balanced equationwill be:
2NH₄NO₃ = 2N₂ + O₂ + 4H₂O.
Delta H = -87.37 kJ/mol
454g / 80g/mol = 5.68 mols NH₄NO₃
N₂: NH₄NO₃ = 4 : 4, so 5.68 mols of N₂ formed.
O₂: NH₄NO₃ = 3 : 4 = x : 5.68, x = 4.26 mols O₂ formed.
So at 1 atm and 25 C, a mol of any ideal gas is 24.5 L. 24.5(5.68 + 4.26) = 243.5
Lb) The volume of NH₄NO₃ is 454g / 1.725g/mL = 263.2 mL = 0.2632 L
The volume increased by a factor of 243.5 / 0.2632 = 925.1