Question

A sample of 0.100 g of propane is burned with excess oxygen with a calibrated calorimeter constant pressure, whose calorific capacity is 520 J. ° C-1. This experience calorimeter temperature has risen 9.62 ° C. Using the data presented, the enthalpy of combustion propane kJ.mol-1 is approximately: Data: molar mass (g mol-1): M 1 = C = 12 (please explain your answer)

(A) -220. (B) -800. (C) -1500. (D) -2200. (E) -5000.

Answer 1

Number of moles of propane = Amount taken / Molar mass of propane = 0.1/44 = 2.27 10^-3 moles

Heat released to the calorimeter by combustion of propane = calorimeter constant Rise in temperature = - 520 J/⁰C 9.62 ⁰C = - 5.0024 kJ (negative since heat is released)

Heat released per mole of propane burnt = Heat released to the calorimeter by combustion of propane / number of moles of propane = - 5.0024 kJ / 2.27 10^-3 moles = - 2203.7 kJ / mole

Therefore, the enthalpy of combustion propane is approximately - 2200 kJ/mole i.e. OPTION C.