Answer to Question #263619 in General Chemistry for atenz

Question

The half-life of Cesium-137 is 30 years. Suppose the intial radioactivity of a sample is 170-Bq.

i. What is the radioactivity after 8 years? (give the answer with accurancy of 2 decimal places)

ii. After how long will the radioactivity be 18 Bq? (give the answer as number of years with accurancy of 1 decimal place )

  

Answer 1

Mass after t years

i)The formula for calculating the amount remaining after a number of half-lives, n

 is

where

A₀ is the initial amount,

A is the amount remaining and

n=t/t_½

This gives

=141.09

ii)

(19/170) times 30

=3 years