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Radium-221 has a half-life of 30 sec. How long will it take for 76% of a sample to decay? (Round your answer to the nearest whole number.)

 Oct 15, 2020
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amountleft = amount (1-.5)n        Where n = number of half lifes     amount left = 1 - .76 = .24

.24 = (1-.5)n

.24 = .5n        Log both sides

log .24 = n log .5

 

log .24 / log .5 =  n

n = 2.0589 half lifes = 61.77 seconds 

 
 Oct 15, 2020
edited by ElectricPavlov  Oct 15, 2020

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