A bomb calorimeter, or constant volume calorimeter, is a device often used to de

Question

A bomb calorimeter, or constant volume calorimeter, is a device often used to determine the heat of combustion of fuels and the energy content of foods. Since the "bomb" itself can absorb energy, a separate experiment is needed to determine the heat capacity of the calorimeter. This is known as calibrating the calorimeter. In the laboratory a student burns a 0.450-g sample of para-toluic acid (C_8 H_8 O_2) in a bomb calorimeter containing 1180. g of water. The temperature increases from 25.00 degree C to 27.20 degree C. The heat capacity of water is 4.184 J g^-1 degree C^-1. The molar heat of combustion is-3862 KJ per mole of para-toluic acid. C_8 H_8 O_2 (s) + 9 O_2 rightarrow 8 CO_2 (g) + 4 H_2 O (1) + Energy Calculate the heat capacity of the calorimeter. heat capacity of calorimeter = J/degree C

Explanation / Answer

In calorimeter experiment

heat given by combustion of sample = heat absorbed by calorimeter + water

thus heat given by sample = mass x molar heat of combustion x rise in temperature/molar mass

= 0.450 gx3862 x1000J x2.2 K/ 136g/mol

= 12778.6J

heat absrbed by water = mass x specific heat x rise in temperature

=1180g x 4.184J /g.C x 2.2 C

= 10861.664 J

heat absorbed by calorimeter = heat capacity s rise in temperature

= heat capacity x 2.2C

Now 12778.6J = 10861.664 J + heat capacity x 2.2C

Thus heat capacity = 871.35 J

The heat capacity of calorimeter = 871.35 J/C

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