Question

The average banana contains 0.436 g of potassium, and 0.012% of naturally occurring potassium is 40K, which has a half-life of 1.248 × 10^9 years and an atomic mass of 39.964 u. What is the activity of a freshly picked bunch containing three bananas?

The activity is the number of 40K decays that occur per unit time. Activity is commonly measured in units of Becquerel (Bq), which is defined as decays per second. Recall that the atomic mass unit u = 1.66 × 10^-24 g.

Answer 1

The number of the moles presented in the001 290 of 0.436 g of the potassium is. 0.012 m 100 JM 0.012 0.436 g 100 1 g/mole 39.964 u = 1.3098 10-6 mole The number of potassium atoms presented in the 0.436 g of potassium is, (1.309×10-6 mole) (6.023×1023 atoms/mole 7.88x107 atoms The activity of the potassium is, 0.693 1/2 0.693 (7.88x10" atoms) 365 day 24 h 3600s 1 y 1 day 1h 1.248x109 y 1 Bq 1 decay/s 13.88 decays/s 13.88 Bq The activity of the three bananas is, -3(13.88 Bq) 41.6 Bq