The curie (Ci) is a commonly used unit for measuring nuclear radioactivity: 1 curie of radiation is equal to 3.7 X 1010 decay events per second.
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?