Question

The mass of the radioactive isotope sodium-24 in a sample is initially measured at 5 milligrams. If the mass of the sodium-24 decreases by 50% every 15 hours, which of the following is closest to the mass of the sodium-24 in the sample 10 hours after the initial measurement?

Answer 1

Explanation:

Radioactive elements decay exponentially so we have the equation

5(x)^15 = 2.5 where x is the decay constant

Solving for x

x^(15) = 2.5/5 = 0.5

15 lnx = ln 0.5

ln x = ln 0.5 / 15 = -0.04621

x = 0.9548

So after 10 hours there ar

5(0,9548)^10

= 3.15 mg to nearest hundredth.