In a bomb calorimeter, the heat of reaction measured corresponds to the change in
- A. enthalpy, since the pressure is constant
- B. internal energy, since the volume is constant
- C. entropy
- D. free energy
Explanation
A bomb calorimeter is a sealed rigid vessel, so the volume cannot change, no expansion work is done and all the energy released appears as heat, which equals the change in internal energy. A reaction in an open vessel is at constant pressure and gives the enthalpy change instead. The two differ only by the work done pushing back the atmosphere.