We’re being asked to determine the mass of arsenic–74 remaining after 54 days if there are 2.3 mCi (millicurie) of 74As initially.
Recall that radioactive/nuclear decay of isotopes follows first-order kinetics, and the integrated rate law for first-order reactions is:
[N]t = concentration at time t
k = decay constant
t = time
[N]0 = initial concentration.
Also, recall that half-life is the time needed for the amount of a reactant to decrease by 50% or one-half.
The half-life of a first-order reaction is given by:
The half-lives of different medical radioisotopes are given in the table below. If the initial amount of arsenic-74 is 2.3 mCi, how much arsenic-74 (mCi) is left in the body after 54 days?
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