Answer:
0.3967mg of sodium-24 are left
Explanation:
If the half life of radioactive element (which is sodium-24 here) is [tex]T_{1/2}[/tex], then at the end of this time the number of atoms in the sample will become half i.e. 1/2 .
if the original amount of atoms is N°. The formula for calculating the remaining atoms (N) left in the sample after t half lives would be:
[tex]N=N^{o} * (1/2)^{t}[/tex]
Here, in this question,
Given amount of sodium-24 = N° = 13 grams
Half life of sodium-24 = t = 15
and Remaining amount of sodium after 45 hours = N = ?
Therefore, using the given Forumla:
[tex]N=\frac{13}{2^{15} }[/tex]
[tex]N= 3.967*10^{-4} g\\ N=0.3967 mg[/tex]
