rning.com/ibiscms/mod/ibis/view.php?id-4941063 uestion 3 of 1 Sapling Learning t

Question

rning.com/ibiscms/mod/ibis/view.php?id-4941063 uestion 3 of 1 Sapling Learning this quetionhes ben custorminedby Paul smithson at Rerea College Cesium-137 was produced in nuclear explosions and was deposiled throughout the Northem Hemisphere during the 1950s and '60s as a result of atmospheric testing of nuclear weapons. At the height of Saviet testing in 1961, it is estimated that fallout by years end from their weapons tests alone deposited about 160 milliCuries (mCi) per square mile in the continental USA (milliCurie is one of several measures of radioactive decay rates). How many mCi/mi2 would remain at the er end of 2001? Half-life of Cs-137 is 30.2 Number Gve Up& View Solution Check Answer NetExi Previous Hint @10- Kinetics-pheno.311 @ R1 @Berea College-c.,..Netflix-Google C.- e F9 F8 F7 F6 F5 F3 F4 F2 8 8

Explanation / Answer

Given,

half-life t1/2 for Cs-137 = 30.2 years

rate constant k = ln2/t1/2

                         = 0.693/30.2

                         = 0.023 year-1

with,

[Cs-137]o = 1.60 mCi/mi^2

[Cs-137] after t=40 years = ?

t = 40 years

using first-order reaction kinetics

ln[Cs-137] = ln[Cs-137]o - kt

ln[Cs-137] = ln(1.60) - 0.023 x 40

after t = 40 years,

amount Cs-137 remained = 0.640 mCi/mi^2               

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