A 1.000 gram sample of the rocket fuel hydrazine (N2H4) is burned in a bomb calorimeter. The temperature rises from 24.62°C to 28.16°C. The heat capacity of the calorimeter (including the water) is 5860 J/°C. Calculate the molar heat of combustion of hydrazine, in kJ/mole.

Answer 1

molar mass of N2H4 = 28+4 = 32 grams/mol
so one gram is (1/32) mol
let joules/mol = x
then
(1/32) mol * x Joules/mol = 5680 Joules/deg * (28.16 - 24.62) deg
so
x = 32 *5680 * (28.16-24.62) Joules/mol
divide by 1000 to get Kilojoules/mol