Question

I did a lab using the bomb calorimeter and my experimental value for heat of formation and heat of combustion are way higher than my literature value. what could be the reason why? I want to know what could have cause me to get such high values. they are several folds higher.

Answer 1

The amount of heat generated or absorbed in a chemical reaction can be studied using a calorimeter.  There are two types of calorimeters: constant-pressure and constant-volume.^2,3 In the constant-volume calorimeter ,the reaction in the bomb takes place at constant volume, the heat that is generated by the reaction (mostly exothermic reactions are studied in a constant volume calorimeter) is actually the change in the internal energy (ΔU) for the reaction. In a constant-pressure calorimetry experiment, like the one that you will be performing, the energy released or absorbed is measured under constant atmospheric pressure. Some other experimental problems with real calorimeters that we need to account for are: 1) real calorimeters can absorb heat, and 2) although the species that undergo the chemical change result in a release/absorption of thermal energy, it is the entire solution that changes its temperature