We can determine [A]t, but lack the value of k.
k can be obtained from the equation of half-life for 1st order reactions:
Step 1: We rearrange the half-life equation to solve for k :
Step 2: We convert the time elapsed to minutes:
Step 3: We determine [A]t in the 1st Order Rate Law:
ln [A]t = -2.119728
Ln has a base of e. When you divide a number by ln you will take e to the power of the number.
Fluorine-18 is a radioactive isotope that decays by positron emission to form oxygen-18 with a half-life of 109.7 min. (A positron is a particle with the mass of an electron and a single unit of positive charge; the equation is 9 18F⟶ 8 18O + +10e)
Physicians use 18F to study the brain by injecting a quantity of fluoro-substituted glucose into the blood of a patient. The glucose accumulates in the regions where the brain is active and needs nourishment.
(b) If a sample of glucose containing radioactive fluorine-18 is injected into the blood, what percent of the radioactivity will remain after 5.59 h?
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Our data indicates that this problem or a close variation was asked in Chemistry - OpenStax 2015th Edition. You can also practice Chemistry - OpenStax 2015th Edition practice problems.