Iron-59 has a half-life of 45.1 days. how old is an iron nail if the fe-59 content is 25% that of a new sample of iron? show all calculations leading to a solution.

90.2 days

Explanation:-

Radioactive decay follows first order kinetics.

Half-life of Iron-59 = 45.1 days

N = amount left after time t=

= initial amount  = a

= rate constant=

t= time  = ?

Thus the iron sample is 90.2 years old.

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