The JAVA applet below simulates two thermodynamic processes, a constant volume process and a constant pressure process. The thermodynamic system in each process is one of the two chemical reactions

The gaseous reactions take place at 25^oC in a cylinder with a movable piston or a cylinder with a fixed volume. Select one of the two reactions and the number of moles of A or D. Click the "Constant Volume" or "Constant Pressure" button to set the reaction conditions. Allow the reaction to go to completion. Click the "Stop" button to end the animation and view the heat change for the reaction.

   The "Constant Temperature" bath is a very large reservoir which can gain or lose heat without a significant change in temperature. Heat is absorbed from or lost to the "Constant Temperature" bath in order to maintain the system at 25^oC during the reaction. The magnitude of heat added to or remove from the "Constant Temperature" bath is equal in magnitude to the heat change for the reaction but opposite in algebraic sign.

    Use the applet in the design and performance of experiments to answer the following questions. See the Tutorial for Experiment: Thermochemistry II for an example and help.

1. Which reaction is endothermic?
2. How does the volume change when the A + B reaction is carried out under the conditions of constant pressure and temperature? Give an explanation for the observed change in volume.
3. How does the volume change when the D + D reaction is carried out under the conditions of constant pressure and temperature? Give an explanation for the observed change in volume.
4. When the endothermic reaction is carried out under the condition of constant volume
, is the amount of heat absorbed greater or less than the amount of heat absorbed under the condition of constant pressure? Give an explanation for the observed difference in heat absorbed.
5. When the exothermic reaction is carried out under the condition of constant volume
, is the amount of heat evolved greater or less than the amount of heat evolved under the condition of constant pressure? Give an explanation for the observed difference in heat evolved.
6. What is the change in enthalpy, DH, for the first thermochemical equation?
7. What is the change in internal energy, DE, for the second thermochemical equation?.

    If you have preformed all of the experiments, answered all of the questions, and completed the report to be submitted for credit, then you may check the Answers to Thermochemistry II Questions