Question

Bi−210 is a beta emitter with a half-life of 5.0 days. Part A If a sample contains 1.8 g of Bi−210 , how many beta emissions would occur in 10 days?

Answer 1

no. of particle in 1.8 g Bi = mass /mole x 6.022 x 10²³ atoms/mole

= 1.8g / 210 g/mol x 6.022 x 10²³ particles/mole = 5.162 x 10²¹ atoms

half life = 5 days

In five days no. of remaining molecules will be =  5.162 x 10²¹ x 0.5 = 2.581 x 10²¹

no. of atoms left unemitted =  5.162 x 10²¹- 2.581 x 10²¹ = 2.581 x 10²¹

In next 5 days it will also become half = 2.581 x 10²¹ x 0.5 = 1.290 x 10²¹ atoms left

total no. of emissions = 5.162 x 10²¹ - 1.290 x 10²¹ = 3.872 x 10²¹ emissions