Question

Phosphorus-32 has a half-life of 14.3 days. how many grams of phosphorus-32 remain after 71.5 days if you start with 4.00 grams?

Answer 1

Answer : 0.125 g

Explanation : If you are calculating the half life of P-32 which has half life of 14.3 days and you want to calculate how many grams are remaining after 71.3 days if yo are starting with 4 g?

starting you can calculate the number of half life P-32 undergoes first,

which is  n = 71.5 / 14.3 = 5 days.

now, to calculate the remaining mass,

$m_{remaining} = (\frac{initial mass}{2 X 2X 2X2 X2 } ) = (\frac{initial mass}{ 2^{5} } )$

= $= \frac{4 g }{ 2^{5} } = 0.125 g$