what is ΔE of combustion of octane in a bomb calorimeter

Question

a bomb calorimeter is used to determine the amount of energy liberate when a sample of octane is combusted. the bomb calorimeter is calibrated by combusting 7.62 g of methane (CH4, MW=16.0 g/mol, ΔEcomb= -902 kJ/mol) which leads to a temperature change of 42.2 C.

after the calibration of the bomb you load 3.10 g of octane into the same calibrated colorimeter and perform your combustion experiment. during this experiment, there is a recorded increase of temperature of 14.6 C.

what is the ΔE of the combustion for octane (MW= 114. g/mol)?

Answer 1

Determine Ccal (specific heat of the calorimeter):

7.62 g CH₄ x 1mole CH₄/16.0 g = 0.4763 mole

0.4763 mole x 902 kJ/mol = 430 kJ

430 kJ/42.2ºC = 10.2 kJ/degree

For combustion of octane:

14.6 degrees x 10.2 kJ/degree = 149 kJ

3.10 g x 1 mol/114 g = 0.0272 moles octane

∆E_comb = 149 kJ/0.0272 moles = -5478 kJ/mole