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J. W. Hill, R. H. Petrucci, T. W. McCreary, & S. S. Perry General Chemistry 4th edition

Problem 17.79

Following are values of Kp at different temperatures for the reaction, 2 SO2(g) + O2(g)2 SO3(g). At 800 K, Kp = 9.1×102; at 900 K, Kp = 4.2×101; at 1000 K, Kp = 3.2; at 1100 K, Kp = 0.39; and at 1170 K, Kp = 0.12. Construct a plot to determine Ho for this reaction.




Answer:

The van't Hoff equation isso the slope of the ln Keq versus 1/T plot equals –Ho/R.

The slope of the plot = 22700 so Ho = –R×slope = –(8.314)×(22700) = –189000 J/mol = –189 kJ/mol