Solved: Using the Integrated First-Order Rate LawThe

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Problem 1PE

Using the Integrated First-Order Rate Law

The decomposition of a certain insecticide in water at 12 °C follows first-order kinetics with a rate constant of 1.45 yr-1. A quantity of this insecticide is washed into a lake on June 1. leading to a concentration of 5.0 x 10-7 g/cm3. Assume that the temperature of the lake is constant (so that there are no effects of temperature variation on the rate), (a) What is the concentration of the insecticide on June 1 of the following year? (b) How long will it take for the insecticide concentration to decrease to 3.0 x 10-7 g/cm3?

At 25 °C. the decomposition of dinitrogen pentoxide. N2O5(g). into NO2(g) and O2(g) follows first-order kinetics with k = 3.4 x 10-5 s-1. A sample of N205 with an initial pressure of 760 torr decomposes at 25 °C until its partial pressure is 650 torr. How much time (in seconds) has elapsed? (a) 5.3 x 10-6 (b) 2000 (c) 4600 (d) 34,000 (e) 190,000