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Solution to Question # 3; lecture 5
How long will a
60
Co source be useful if it can be used until the γrays it
produces reach 70 percent of the original intensity?
60
27
Co decays with a
half–life of 5.30 years to produce
60
28
Ni.
Convert given halflife (5.30 years) to rate constant k by using this equation:
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Unformatted text preview: k = ln 2 / t 1/2 = ln 2 / 5.30 y = 0.693/5.30 y = 0.131 /y Use the integrated rate equation to obtain time t since you know k and N /N ( = 100/70l; from question): ln (N/N o ) =  k t => ln (N /N) = kt => t = [ln (N /N)]/k = [ln (100/70)] / 0.131/y = 2.74 y...
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This note was uploaded on 02/06/2012 for the course CHM 115 taught by Professor Towns during the Spring '08 term at Purdue UniversityWest Lafayette.
 Spring '08
 Towns
 Chemistry, HalfLife

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