How do I find the heat of combustion of the unknown hydrocarbon?

Question

When 0.0801 mol of an unknown hydrocarbon is burned in a bomb calorimeter, the calorimeter increases in temperature by 2.19°C. If the heat capacity of the bomb calorimeter is 1.229 kJ/°C, what is the heat of combustion for the unknown hydrocarbon?

Answer 1

q_rxn = – C_cal · (delta)T_cal

q_rxn = – 1.229 kJ/°C · 2.19°C

q_rxn = – 0.561 kJ

Heats of combustion are almost always expressed in kJ/mol, so…

– 0.561 kJ / 0.0801 mol = –7.01 kJ/mol