Question

calculator sodium-24 has a half - life of 15 hours. how many grams of a 900 g sample will remain after 90 hours? 7.03125 g 7.5 g 14.0625 g 28.125 g

Explanation:

Step1: Calculate number of half - lives

The number of half - lives $n=\frac{90}{15}=6$.

Step2: Use half - life formula

The formula for radioactive decay is $A = A_0\times(\frac{1}{2})^n$, where $A_0 = 900$ g (initial amount) and $n = 6$. So $A=900\times(\frac{1}{2})^6$.

Step3: Calculate the remaining amount

$A = 900\times\frac{1}{64}=\frac{900}{64}=14.0625$ g.

Answer:

14.0625 g