University:
The Pennsylvania State University
Course:
CHEM 450 | Thermodynamics
Academic year:

2024
Views:

133

Pages:

2
Author:

Alexis H.

Problem Set #45 Assigned: April 19, 2024 Due: April 22, 2024 at 2:30 pm (1) Consider the following three gas phase reactions: (i) A B, (ii) 2A B, and (iii). A 2B. Explain what happens to the concentrations of A and B as the pressure is changed under conditions of constant temperature. Invoke LeChatelier’s principle and the equilibrium constant in your explanations. (2) In class we found that the equilibrium constant doesn’t change as a function of pressure. (a) Should this result represent an ideal gas or a real gas? (b) Explain why differences between real and ideal gases may arise as the pressure is raised. (3) Consider the following chemical reaction: H2CO(g) CO(g) + H2(g). How does the part of the equilibrium constant that just contains the mole fractions of the gases change if the total pressure of the system is doubled? (Hint: separate the pressure and the mole fraction portions of the equilibrium constant to answer this questions). (4) The equilibrium constant for the gas phase isomerization of borneol to isoborneol is 0.106 at 503K. A mixture initially consisting of 7.50 g borneol and 14.0 g isoborneol is allowed to come to equilibrium at 503 K in a 5 L container. Find the mole faction of each of the two compounds at equilibrium. Note that the molecular weight of both compounds is 154.253 g/mol. 1. (i) When the pressure changes the concentration will remain the same because the two components are in equilibrium with each other and for the two to stay in equilibrium what happens to one must happen to the other. (ii) When the pressure changes the concentration of B changes more than that of A because A has a greater concentration, to keep them in equilibrium B must rise a greater amount than A to keep it in equilibrium (iii) When the pressure changes the concentration of A has to rise more than A since the concentration has to equal that of B and B is twice that of A 2. It applies to a real gas. Di erences arise because in real gases there is not a single amount of pressure is left in the expression so changing the pressure makes no di erence to the concentration expression. 3. The concentrations will not change if the pressure is doubled because the pressure ensures that the system maintains equilibrium, leaving the products and reactants equal to each other. 4. Xp x x k It fgimo 154 gimo 0.0487mol 0.0907mol 0.0487 0.0907 0.1394 borneol so borneol isoborneo 0.106 borneol 0.106 isoborneo borneol iso borneol borneol 0.106 1106 isoborneo 8 01394 01394 01259 0.106 01259 0.0134 mF 89344mmol 01394 borneol borneol borneol borneol 0.902 0.096