homework_452hmwk7 - 1 2010 Sarah L. Keller Chem 452...

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Unformatted text preview: 1 2010 Sarah L. Keller Chem 452 Homework Set #7 This homework starts hard and gets easier. Ive written long hints. You have NO homework due Feb. 25-26; relax and catch up in other classes. If you start this set early, begin with problems 1-5. Midterm #2 (on Feb. 22) will cover topics through this assignment, but no further. The exam is cumulative only in as much as the homeworks have been cumulative. Homework set 7 may not be graded before the exam, so if you want to study from it, you may want to make a copy for yourself. The first page of the exam with equations will be posted online. You will be given the same table of constants for water as on midterm 1. As before, you are not allowed a page of your own notes. --------------------------------------------------------------------------------------------------------------- 1) The shells of marine organisms contain CaCO 3 largely in the crystalline form known as calcite. There is a second crystalline form of CaCO 3 known as aragonite. (From Tinoco, problem 3.12) Property at 298K calcite aragonite H f ( kJ / mol )-1206.87 -1207.04 G f ( kJ / mol )-1128.76 -1127.71 S ( J / molK ) 92.88 88.70 C p ( J / molK ) 81.11 81.25 Density (g/cm 3 ) 2.710 2.930 (a) Based on the thermodynamic and physical properties given for these two crystalline forms, would you expect calcite in nature to convert spontaneously to aragonite given sufficient time? Briefly justify your answer. (b) Explain briefly whether the conversion proposed in part (a) will be favored or opposed by increasing the pressure. (c) What pressure is sufficient to make this conversion spontaneous at 25C? Ans: ~3.8 x 10 8 Pa (d) Will increasing the temperature favor the conversion? Explain briefly. 2) Consider a system that undergoes a phase change from phase to phase at an equilibrium temperature T m and equilibrium pressure P m . At these equilibrium conditions, the heat absorbed per mole of material undergoing this transition is q m , and there is a molar volume change of V m ....
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This note was uploaded on 03/04/2010 for the course CHEM CHEM 452 taught by Professor Robinson during the Winter '09 term at University of Washington.

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homework_452hmwk7 - 1 2010 Sarah L. Keller Chem 452...

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