Determination of the enthalpy of combustion with a calorimetric bomb

Principle

The bomb calorimeter is used to completely burn substances in an excess of oxygen. The heat of combustion released is absorbed by the calorimetric vessel in which the bomb is immersed, and results in a temperature increase ΔT. The heat capacity of the system is first determined by adding a defined amount of heat from the combustion of benzoic acid. The combustion of the naphthalene is subsequently performed under the same conditions.

Benefits

• Good and reproducible results due to temperature control in the experiment.
• Only a small amout of chemicals is need for the experiment due to the good heat capacity of the calorimeter.

Tasks

1. Determine the enthalpy of combustion of naphtalene using a bomb calorimeter.
2. Calculate the enthalpy of formation of naphthalene from the enthalpy of combusting unsing Hess' law.

Learning objectives

• First law of thermodynamics
• Hess' law of constant heat summation
• Enthalpy of combustion
• Enthalpy of formation
• Heat capacity

Necessary accessories

• Precision balance 620g/0.001g
• Precision balance 6200g/0.01g