Measuring Activation Energy * The determination of activation energy requires kinetic data, i.e., the rate constant, k, of the reaction determined at a variety of temperatures. The student then constructs a graph of ln k on the y-axis and 1/T on the x-axis, where T is the temperature in Kelvin. The data points should fall along a straight line, the slope of which is equal to (-Ea/R), where R is the ideal gas constant.

Iodine-Clock Activation Energy * The plot of (ln k) vs. (1/T) for the iodine clock reaction should reveal a slope of about -6230. Thus, (-Ea/R) = -6230. Using an ideal gas constant of R = 8.314 J/K.mol gives Ea = 6800 * 8.314 = 51,800 J/mol, or 51.8 kJ/mol.

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