Question

A 50.6 mg sample of sodium perchlorate contains radioactive chlorine-36 (whose atomic mass is 36.0 amu). If 29.6% of the chlorine atoms in the sample are chlorine-36 and the remainder is naturally occurring nonradioactive chlorine atoms, how many disintegrations per second are produced by this sample? The half-life of chlorine-36 is 3.5*10^5 yr.

Answer 1

moles NaClO4 = grams/molar mass
moles Cl atoms = moles NaClO4.
# Cl atoms = moles Cl atoms x 6.02E23 atoms/mol.
Multiply by 0.296 to find the number that are radioactive.
rate = k*No where No = number Cl atoms
k can be determined from k = 0.693/t_1/2 and the units are Yr^-2 since the half life is in years.
Therefore, the rate you calculate will be the decays per year. Convert that to dps.