tutorial 3 solutions

tutorial 3 solutions - CHEM 1E03 TUTORIAL #3 Solutions _ 1....

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CHEM 1E03 TUTORIAL #3 Solutions _____________________________________________________________________ Page 1 of 4 1. 0.400 mol of a gas with a heat capacity of 20.8 J/mol·K, is heated at constant pressure so that its temperature increases from 21.00 ºC to 79.83 ºC. As a result, the gas expands from 10.0 L to 12.0 L against an external pressure of 0.965 atm. What is the energy change, U (in J), for the gas? A) +1.03   B) +6.85   B) –2.94   D +2.94   E) -3.45   U = q + w q = 0.400 mol 20.8 J/mol.K (79.83-21.00) K = 489.46 J (q is absorbed, q > 0) w = -P   V = 0.965 atm 2.0 L (8.3144/0.08206 J/atm.L) = -195.68 J (gas expands, w <0) U = + 293.78 J = + 2.94 10 2 J (with 3 sigfigs) 2. For the process N 2 (g) N 2 (l) at 77 K, which one of the following statements is false? (All statements refer to the system.) A) V < 0 C) q > 0 False D) H 0 D U 0 E) w > 0 For all pure substances, the enthalpy of the gas is always larger than the enthalpy of the liquid. Hence in the transformation from nitrogen gas to nitrogen liquid, heat is released and q < 0. 3. Use enthalpies of formation (found in Appendix D of your textbook) to calculate the
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tutorial 3 solutions - CHEM 1E03 TUTORIAL #3 Solutions _ 1....

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