Chemistry 342 Fall 2001 First Hour Exam, Exams of Physical Chemistry

Download Chemistry 342 Fall 2001 First Hour Exam and more Exams Physical Chemistry in PDF only on Docsity! Chemistry 342 Fall 2001 First Hour Exam 1. (20 pts) Use the following information to calculate the enthalpy of formation of SO3(g). PbO(s) + S(s) + 3/2 O2(g) Ø PbSO4(s) DH = -39.56 kJ/mol PbO(s) + H2SO4∏5H2O(liq) Ø PbSO4(s) + 6H2O(liq) DH = -5.57 kJ/mol SO3(g) + 6H2O(liq) Ø H2SO4∏5H2O(liq) DH = -9.82 kJ/mol 2. (24 pts) The 3D Maxwell-Boltzmann distribution is given by: , 4 )( 22 / 3 2 α απ ve v vf −= where ½ ma2 = kT. a. Determine the average value of the kinetic energy at temperature T. (You must show all your work to get any credit.) b. What fraction of the molecules have a kinetic energy greater than the average value? (It is sufficient to set up the problem without actually working out the answer in detail.) Some useful integrals: ∫ ∞ + − −⋅⋅⋅⋅⋅= 0 1 2 2 )12(5312 aa n dxex nn axn π ∫ ∞ + −+ = 0 1 12 2 !2 n axn a n dxex