In order to calibrate a constant volume bomb calorimeter, the combustion of (7.450x10^-1) g of benzoic acid, C6H5COOH, was observed to cause the temperature in the calorimeter to rise from 25.000 to (2.87000x10^1) oC. The energy of combustion of benzoic acid, ΔU, is -3226.7 kJ mol-1. What is total heat capacity (C) of the calorimeter (including all its contents) in kJ oC-1?
Molar mass of benzoic acid is 122.12 g/mol
The energy of combustion of benzoic acid, ΔU, is -3226.7 kJ mol-1 x (122.12 g/mol) = 394x103 kJ/g
for 1 g of benzoic acid the heat evolved is 394x103 kJ
for 0.7450 g of benzoic acid the heat evolved is 0.7450 x 394x103 kJ = 293530 kJ
So this amount is utilized to raise the temperature of the solution in the calorimeter.
So 293530 kJ = total heat capacity x change in temperature
= total heat capacity x (28.7 - 25.0 ) oC
total heat capacity = 79332 kJ/oC
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