1. The radium isotope 223Ra, an alpha emitter, has a half-life of 11.43 days. You happen to have a 1.0 gg cube of 223Ra, so you decide to use it to boil water for tea. You fill a well-insulated container with 100 mL of water at 16∘∘ and drop in the cube of radium. How long will it take the water to boil?

2. The half-life of 60Co is 5.27 years. The activity of a 60Co sample is 3.80×10⁹ Bq . What is the mass of the sample?