The curie (Ci) is a commonly used unit for measuring nuclear radioactivity: 1 curie of radiation is equal to 3.7 1010 decay events per second (the number of decay events from 1 g of radium in 1 s).
(a) What mass of Na238SO4 has an activity of 10.0 mCi? Sulfur-38 has an atomic mass of 38.0 and a half-life of 2.87 h.
(b) How long does it take for 99.99% of a sample of sulfur-38 to decay?