ThermoChemistry (chapt. 9)

In this Chapter, we only do coffee cup calorimeter but not bomb calorimeter. Our group want to present the bomb calorimeter and the function. Below is the picture of bomb calorimeter :

1. Purpose of Bomb Calorimetry Experiments

Bomb calorimetry is used to determine the enthalpy of combustion, D_combH, for hydrocarbons:

The bomb calorimeter consist primarily of the sample, oxygen, the stainless steel bomb, and water.

The dewar prevents heat flow from the calorimeter to the rest of the universe.Since the bomb is made from stainless steel, the combustion reaction occurs at constant volume and there is no work.Recall that DU=q_v is the heat flow under constant volume conditions, whereas DH=q_pis the heat flow under constant pressure conditions. The difference between these two situations is that pV work can be done under constant pressure conditions, whereas no pV work is done under constant volume conditions.

Consider the case where Dn_gas > 0. i.e., the system expands during the reaction. The same amount of energy is released by the reaction under both sets of conditions.

2. Application of D_combH

In addition to measuring the energy release of one particular reaction, calorimetry is an important tool for determining the enthalpy of formation for the compound under study. This information can then be applied to any reaction involving the compound.