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Survey of Physical Chemistry Assumptions

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Survey of Physical Chemistry 5th Edition

State all assumptions (e.g. ideal gas etc).

Using the tables in your text, calculate the following reaction under constant pressure (1 bar) at 298 Kelvin, calculate th e Î"S0 , Î"HO, and Î"Go , for the following reaction. Is this reaction spontaneous at room temperature? Can this reaction be shifted from Spontaneous to Nonspontaneous by simply changing the reaction? If yes, determine the pivotal temperature at which the reaction will be spontaneus or non-spontaneous. Please indicate any assumptions (with some type of justification) you are making to simplify your answer.

Na(s) + Cl2(g) ------> NaCl(s)

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See attached- plain text version follows.

The first thing to do is to balance the reaction:
Na(s) + 1/2 Cl2(g) ------> NaCl(s)
You will need the correct stoichiometry to calculate the thermodynamic changes of the reaction.
You can find the data you need in the thermodynamic tables at the back of your book (or check the CRC Handbook of Chemistry & Physics). You will need each species' standard heat of formation (fHO), standard molar entropy (SOm), and standard free energy of formation (fGO). Be sure to get the values for the appropriate state (solid, liquid, gas) of the substance. For these species, the values are (approximately)

Quantity (Units) Na(s) Cl2(g) NaCl(s)
fHO (kJ mol-1) 0 0 -400
SOm (J mol-1 K-1) 50 225 70
fGO (kJ mol-1) 0 0 -375

1. I have rounded all of these value. Remember, my job is to show you how to do this problem, not to do it for you.
2. The standard enthalpies and ...

Solution Summary

A survey of physical chemistry assumptions are examined.