A bomb calorimeter is used to determine the amount of energy liberated when a sa
ID: 1019811 • Letter: A
Question
A bomb calorimeter is used to determine the amount of energy liberated when a sample of octane is combusted. The bomb calorimeter is calibrated by combusting 7.77 g of methane (CH4, MW=16.0g/mol, Ecomb = -902kJ/mol) which leads to a temperature change of 42.8°C.
After the calibration of the bomb you load 3.40 g of octane into the same calibrated calorimeter and perform your combustion experiment. During this experiment, there is a recorded increase of temperature of 15.9°C.
What is the E of combustion for octane (MW = 114 g/mol) in kJ/mol? Please report your answer to the correct number of significant figures.
Explanation / Answer
no of mol of methane = 7.77/16 = 0.486 mol
heat released in the reaction = 902*0.486 = 438.4 kj
q = 438.4 kj
DT = 42.8 C
q = Cp*DT
438.4 = x*42.8
x = Cp = heatcapacity of clorimeter = 10.243 kj/c
form that,
No of mol of octane = 3.4/114 = 0.03 mol
q = Cp*DT
= 10.243*15.9
= 162.9 kj
DE of combustion for octane = 162.9/0.03 = 5430 kj/mol
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