Answer:
The sample has 150 years, 1314000 hours
Explanation:
The element decay follows the first order kinetics law:
ln[Cs-135] = -kt + ln [Cs-135]₀ (1)
Where [Cs-135] is concentration after t time, k is rate constant in time, and [Cs-135]₀ is initial concentration
Half-life formula is:
[tex]t_{1/2} = \frac{ln2}{k}[/tex]
30 years = ln2 / k
k = 0.0231 years⁻¹
Using rate constant in (1):
ln[0.25mg] = -0.0231 years⁻¹×t + ln [8mg]
-3.466 = -0.0231 years⁻¹×t
150 years = t
The sample has 150 years
In hours:
150years × (365days / 1year) × (24hours / 1day) = 1314000 hours
