We’re being asked to calculate the heat of the reaction (qrxn) in a bomb calorimeter. This is given by the equation:
where qcalorimeter = heat absorbed by the calorimeter and qsolution = heat absorbed by the water in the calorimeter.
Expanding this, we have:
Ccal = heat capacity of the calorimeter
m = mass of water (in grams)
c = specific heat capacity of water
ΔT = change in temperature = final T – initial T.
We can’t use the mass of pentane to determine the heat of the reaction needed since the heat capacity of pentane isn’t given. This is why we used the heat absorbed by the calorimeter and the water instead.
A 0.3423 g sample of pentane, C5H12, was burned in a bomb calorimeter. The temperature of the calorimeter and the 1.000 kg of water contained therein rose from 20.22 °C to 22.82 °C. The heat capacity of the calorimeter is 2.21 kJ/°C. The heat capacity of water = 4.184 J/g•°C. How much heat was given off during combustion of the sample of pentane?
1) 8.8 kJ
2) -8.8 kJ
3) 16.6 J
4) 16.6 kJ
5) 3.1415 kJ
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