calorimetry....

Question

When 0.0501 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

The heat of combustion can be determined by knowing the heat capacity of the calorimeter and the change in temperature of the reaction, and is given by q = C_cal x ∆T

q = heat

C_cal = heat capacity of the calorimeter = 1.229 kJ/degree

∆T = change in temperature = 2.19 degrees (exothermic reaction since temperature went up)

q = (1.229 kJ/deg)(2.19 deg) = -2.69 kJ which is the heat of combustion for 0.0501 moles of hydrocarbon

If the question means to ask for the molar heat of combustion, then you would have...

2.69 kJ/0.0501 moles = -53.7 kJ/mole (note a negative sign indicating an exothermic reaction)