Exercise 9 | Chemical Kinetics: Rate Laws

A 2.00 g sample of the radioisotope phosphorus-32 is found to contain 0.250 g of phosphorus-32 after 42.0 days.

Calculate the half-life of this isotope.

Radioactive decay is a first-order process:

ln NN0 = - kt and t1/2 = ln 2k

⇒ t1/2 = - ln 2 × tln NN0

⇒ t1/2 = - ln 2 × 42ln 0.2502.00 = 14.0 days