JAMB Chemistry 2024 Paper

There are several methods of solving this radioactivity problem. One of the easiest is:

$\frac{\text{Original mass}}{2^n}$ = Residual mass

Where n = number of activity = $\frac{\text{exposure time}}{\text{half life}}$

Given:

Original mass = 5g, exposure time = 200 days , half life = 50 days, Residual mass = ?

Substituting all the given parameters appropriately, we have

n = $\frac{200}{50}$

n = 4

$\frac{\text{Original mass}}{2^n}$ = Residual mass

$\frac{5}{2^4}$ = Residual mass

$\frac{5}{16}$ = Residual mass

Residual mass = 0.3125g = 0.31g