a) The radioisotope phosphorus-32 is used in tracers for measuring phosphorus up
ID: 1060952 • Letter: A
Question
a) The radioisotope phosphorus-32 is used in tracers for measuring phosphorus uptake by plants.
The half-life of phosphorus-32 is 14.3 days. How many milligrams of a 98.8 milligram sample of phosphorus-32 will be lost by radioactive decay during 71.5 days?
b) Nitrogen-13 is used in tracers injected into the bloodstream for positron emission tomography (PET).
The half-life of nitrogen-13 is 10.0 minutes. How many milligrams of a 66.1 milligram sample of nitrogen-13 will be lost by radioactive decay during 50.0minutes?
Explanation / Answer
a) firat calculate the rate constant
K = 0.693 / t1/2
K = 0.693 / 14.3
K = 0.0485 days-1
now
K = (2.303 /t) log [A0] / [A]
0.0485 = (2.303 / 71.5) log [98.8] / [A]
1.506 = 1.99 - log [A]
log [A] = 0.485
[A] = 3.05
98.8 - 3.05 = 95.75 mg
mass of sample lost = 95.75 mg
b) K = 2.303 / 10
K = 0.23 min-1
now
K = (2.303 /t) log [A0]/[A]
0.23 = (2.303 / 50) log [66.1] / [A]
4.99 = 1.82 - log [A]
log [A] = -3.17
[A] = 0.0068
mass of sample decomposed = 66.1 - 0.0068 = 66.09 mg
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.