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Unformatted text preview: 1 Exam 1 (PChem for the Biosciences CHM3400), Feb. 7, 2011 Name :_______________________________________ UFID :_____________________ Instructions : Use a pen, NOT a pencil to answer the questions . Fill in your name and UFID above. Give your answers in the blank spaces following each question/sub-question. The total credit for this exam is 100 points . The credit of each sub-question is indicated in bold ( credit ). Numeric values should be given with a sufficient number of digits and the units must be indicated. Useful tables, physical constants and formulae for this test are given with the question or at the end of the exam as an Appendix make sure that you check the content of the Appendix before reading the questions. Be concise with your answers, but remember that you are graded on the information that you put down on paper if intermediate steps in a calculation are missing and the result is incorrect, no credit can be given. Always show the equations and units that you use. Good luck! Short questions : 1. Draw a schematic of how the absolute zero temperature was determined experimentally in the 1800s. (5 pts) V T at constant P Upon extrapolating to zero volume, it is found that there must be a zero volume at T= 0 (Kelvin). 2. In the equation E kin = 3/2 k B T, where does the 3 come from, and why? (3 pts) The 3 is related to the 3 dimensions x,y and z. Since we assume random motion, the average velocity v 2 /3 = v x 2 = v y 2 = v z 2 . 3. Based on the units, explain why PV = work. (4 pts) P in Nm-2 and V in m 3 , so Nm-2 m 3 = Nm (units of work) 2 4. U = w + q = constant, w = constant and q = constant. Fully explain how this statement is (in)correct. (5 pts) U is the internal energy, and hence a state function. Hence, the statement that U = work + heat = constant is correct. However, work and heat are path functions, and hence they are not necessarily constant. They depend on the path that is taken....
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