The rate of photodecomposition of the herbicide picloram in aqueous systems was determined by exposure to sunlight for a number of days. One such experiment produced the following results. (Data from R.T. Hedlun and c.R. Youngson, “The Rates of Photodecomposition of Picloram in Aqueous Systems,” Fate of Organic Pesticides in the Aquatic Environment, Advances in Chemistry Series, #111, American Chemical Society (1972), 1592172.)

Determine the order of reaction, the rate constant, and the half-life for the photodecomposition of picloram.

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Exposure Time, t (days) 0 7 14 21 28 35 42 49 56 [Picloram] (mol L-¹) 4.14 x 10-6 3.70 x 10-6 3.31 x 10-6 2.94 x 10-6 2.61 x 10-6 2.30 x 10-6 2.05 x 10-6 1.82 x 10-6 1.65 x 10-6