bomb.html

Bomb Calorimetry

Here is a schematic drawing of a bomb calorimeter:

The "Bomb" inside is a steel vessel capable of withstanding the large pressure of gas inside as well as the explosive force of the burning reagents inside.

This is a Constant Volume calorimeter since the reaction occurs within a rigid vessel (the bomb) whose volume cannot change.

The heat capacity of the calorimeter is equal to the sum of the heat capacity of the water + the heat capacity of the dry calorimeter (bomb, stirrer, insulated container, etc):

C_calorimeter = C_{dry parts} + C_H₂O

If we know C_calorimeter and measure T, we can obtain the heat change in the calorimeter.

q_calorimeter = C_calorimeter x T

but

E_rxn = q_rxn = - q_calorimeter= - C_calorimeter x T

Example: if a reaction performed in a bomb calorimeter is exothermic then the

heat absorbed by the calorimeter assembly, q_calorimeter is positive (temperature of calorimeter rises)

But this is an exothermic reaction (E_rxn<0) in which no work is done so q_rxn = - q_calorimeter.
               

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