Question

A medical scientist has a 15-gram sample of I-131 and would like to its half-life, in days. He also knows that k = 0.0856.

N = N0e -kt

N0 = 15 grams

N = 7.5 grams

k = 0.0856

t = ?


Find the half-life, in days, of I-131 using the information at the left. Round your answer to the nearest tenth.

Answer 1

Please re-arrange the formula for t

\[N = N_{0}e^{-kt}\]

\[\frac{ N }{ N_{0} } = e^{-kt}\]

\[\ln(\frac{ N }{ N_{0} }) = \ln(e^{-kt})\]

\[Ln(\frac{ N }{ N_{0} }) = -kt \]

\[-k*\ln (\frac{ N }{ N_{0} }) = t \]

Answer 2

Ok

Answer 3

And don't I need to divide 7.5 abd 0.0856

Answer 4

And*

Answer 5

\[-8.56*10^{-2}*\ln (\frac{ 7.5 }{ 15 }) = t\]