A sample of sodium phosphate, Na3PO4, weighing 54.5 mg contains radioactive phosphorus-32 (with mass 32.0 amu). If

Question:

A sample of sodium phosphate, Na3PO4, weighing 54.5 mg contains radioactive phosphorus-32 (with mass 32.0 amu). If 15.6% of the phosphorus atoms in the compound is phosphorus-32 (the remainder is naturally occurring phosphorus), how many disintegrations of this nucleus occur per second in this sample? Phosphorus-32 has a half-life of 14.3 d.