81. Suppose a rock sample initially contains 250 grams of theradioactive substance unobtainium, and that the amountof unobtainium after t years is given by an exponentialfunction of the form S(t) = Aek. The half-life of unob-tainium is 29 years, which means that it takes 29 years forthe amount of the substance to decrease by half.(a) Find an equation for the exponential function S(t).(b) What percentage of unobtainium decays each year?(c) How long will it be before the rock sample containsonly 6 grams of unobtainium?

All radioactive decays follow first-order kinetics where the rate of reaction is directly…

Answered: 81. Suppose a rock sample initially…

Physical Chemistry

2nd Edition

ISBN:9781133958437

Author:Ball, David W. (david Warren), BAER, Tomas

Publisher:Ball, David W. (david Warren), BAER, Tomas

Chapter20: Kinetics

Section: Chapter Questions

Problem 20.88E

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The rate constant for the radioactive decay of 14C is 1.21104 year-1. The products of the decay are nitrogen atoms and electrons (beta particles): C614N714+e rate =k[C614] What is the instantaneous rate of production of N atoms in a sample with a carbon-14 content of 6.5109M?
Recently, the skeleton of King Richard III was found under a parking lot in England. If tissue samples from the skeleton) contain about 93.79% of the carbon-14 expected in living tissue, what year did King Richard III die? The half-life fur carbon-14 is 5730 years.
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The rate of photodecomposition of the herbicide piclo- ram 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 tbe Aquatic Environment, Advances in Chemistry Series, #111, American Chemical Society (1972), 159—172.) Exposure Time, t (days) [Pidoram] (mol L_1) 0 4.14 X 10-6 7 3.70 X 10-6 14 3.31 X 10-6 21 2.94 X 10~6 28 2.61 X 10~6 35 2.30 X 10-6 42 2.05 X 10-6 49 1.82 X 10"6 56 1.65 X 10-6 Determine the order of reaction, the rate constant, and the half-life for the photodecomposition of picloram.
The half-life of tritium, 3H, is 12.26 years. Tritium is the radioactive isotope of hydrogen. (a) What is the rate constant for the radioactive decay of tritium, in y1 and s1? (b) What percentage of the original tritium is left after 61.3 years?
Label the elementary processes for the reaction between H2 and O2 see section 20.7 as initiation, propagation, branching, or termination reactions.

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