We’re being asked to determine the mass of Lead–200 remaining after 72.0 hours if there are 3.770 mg of Lead–200 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:
Lead-200 has a half-life of 21.50 hours. Starting with 3.770 mg of this isotope, how much would remain after 72.0 hours?
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