Week 1.
Calculate the fraction of atoms remaining of 24Na (half-life 15 hours) after a decay
interval of 5 hours. What is the half-life of a radionuclide whose disintegration
rate decreased from 2.00 x 104 d/s to 1.26 x 104 d/s in 10 hours?
Rb has 2 naturally occurring isotopes. Calculate the atomic weight of Rb, given that
natural Rb consists of 72.165% 85Rb, and that the atomic masses of 85Rb and
87Rb are 84.9118 and 86.9092 amu respectively.
How many atoms of radioactive 87Rb ( = 1.42 x 10-11 y-1) are there in 2g of granite
containing 75 ppm Rb? (Avogadro's number = 6.023 x 1023). How many of these
atoms will decay in a period of 1 year?