A 0.84 g sample of caffeine, C8H10N4O2, burns in a constant-volume calorimeter that has a heat capacity of 7.85 kJ/K. The temperature increases from 298.30 K to 303.35 K. What is the molar heat of combustion of caffeine (in kJ).

Answer 1

q = 7.85 kJ/K x (303.35-298.30) = 39.01 kJ
So 39.01 x (molar mass caffeine/0.84) = ? kJ/mol caffeine.