Strontium-90 has a specific activity of 5.21 x 10¹² Becquerel and a half-time of 28.79 years.

Calculate the activity of ⁹⁰Sr after 135 years have passed.

Question

Strontium-90 has a specific activity of 5.21 x 10¹² Becquerel and a half-time of 28.79 years.

Calculate the activity of ⁹⁰Sr after 135 years have passed.

| General Chemistry 2

Accepted Answer

Radioactive decay is a first-order process:

ln $(\frac{A}{A_{0}})$ = - kt and t_1/2 = $\frac{\ln 2}{k}$

$\frac{A}{A_{0}}$ = e^-kt = exp $(- \frac{\ln 2 \times t}{t_{1 / 2}})$

A = 5.21 x 10¹² x exp $(- \frac{\ln 2 \times 135}{28.79})$

A = 2.02 x 10¹¹ Becquerel

Final - Question 5 | General Chemistry 2