1 Answer

Nardo · Answer 1 · 2021-12-01T09:58:04+0000

32 days

General formulas used in decay:

$\large{\boxed{\bold{N_t=N_0((1)/(2))^{t/t(1)/(2) }}}$

t = duration of decay

t 1/2 = half-life

N₀ = the number of initial radioactive atoms

Nt = the number of radioactive atoms left after decaying during T time

The half-life of iodine-131 is 8 days

No=80 g

Nt=5 g

$\tt 5=80((1)/(2))^(t/8)\\\\(5)/(80)=(1)/(2)^(t/8)\\\\(1)/(2)^4=(1)/(2)^(t/8)\\\\4=(t)/(8)\rightarrow 32~days$

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