The half-life of carbon-14, an isotope used in archaeological dating, is 5730 ye
ID: 967405 • Letter: T
Question
The half-life of carbon-14, an isotope used in archaeological dating, is 5730 years... What percentage of 14/6C remains in a sample estimated to be 17,000 years old?
The half-life of mercury-197 is 64.1 hours. If a patient undergoing a kidney scan is given 5.0 ng of mercury-197, how much will remain after 4 days? After 34 days?
A solution of selenium-75, a radioisotope used in the diagnosis of pancreatic disease, is found just prior to administration to have an activity of 44 Ci/mL If 4.02 mL were delivered intravenously to the patient, what dose of Se-75 (in Ci) did the patient receive?
Explanation / Answer
1) K = (1/t)ln(a/x)
k = 0.693/5730
= 0.000121 y-1
0.000121 = (1/17000)ln(100/x)
x= 12.8%
remaining % = 12.8%
2)a. k = 0.693/64.1 = 0.011 hr-1
0.011 = (1/(4*24))ln(5/x)
x=remaining = 1.74 %
b
0.011 = (1/(34*24))ln(5/x)
x=remaining = 0.000632 %
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