First, we determine the energy released by the reaction using the heat capacity and change in temperature as such:
Q = cΔT
Q = 32.16 * 0.42
Q = 13.51 kJ
Next, we determine the moles of ammonia formed as the heat of formation is expressed in "per mole".
Moles = mass / molecular weight
Moles = 5/17
Moles = 0.294
Heat of formation = 13.51 / 0.294
The heat of formation of ammonia is 45.95 kJ/mol
Moles of NaN3 at STP = volume of gas / 22.4 = 11.5/22.4 = 0.5mole. Massof NaN3 = moles of NaN3 x molecular weight = 0.5 x 65 = 32.5 grams.
