Question

35. Strotium−90, a radioactive isotope, is a major product of an atomic bomb explosion. It has a half-life of 28.1 yr. (a) Calculate the first-order rate constant for the nuclear decay. (b) Calculate the fraction of 90Sr that remains after 10 half-lives. (c) Calculate the number of years required for 92.3 percent of 90Sr to disappear. (a) yr−1 (b) × 10 (c) × 10 yr

The activity of a radioactive sample is the number nuclear disintegrations per second, which is equal to the first-order rate constant times the number of radioactive nuclei present. The fundamental unit of radioactivity is the curie (Ci), where 1 Ci corresponds to exactly 3.70 × 1010 disintegrations per second. This decay rate is equivalent to that of 1 g of radium−226. The molar mass of Ra−226 is 226.03 g/mol. Calculate the rate constant for the radium decay. × 10 s−1 (Enter your answer in scientific notation.) Calculate the half-life for the radium decay. × 10 s (Enter your answer in scientific notation.) Starting with 2.6 g of the radium sample, what is the activity after 3.0 × 102 yr? Ci

Answer 1