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Unformatted text preview: than decreased) temperature. 53b) You could again do this just by looking in appendix D. Alternatively, you know that at 368.5 K, the process is spontaneous; for convenience, say that G = 0 rather than very slightly > 0 at that temperature. If H were -400 J mol-1 , the process would always be spontaneous, so it must be +400 J mol-1 . Therefore, 0 = 400 - 368.5* S, so S = -400/-368.5 = 1.09 J mol-1 . 62a) The difference between the H vap calculated using the standard values and the actual H vap is the temperature-dependence of H. The standard values are calculated at 25 C, and the process described takes place at 76.5 C. This is an example of how H changes with temperature (actually a relatively large change; most processes will have < 10% change over 100 degree ranges, rather than the 15% or so of this process). 1...
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- Fall '08