Answer:
25 gram left
Explanation:
Given data:
Total mass = 100 g
Half life of radioactive material = 10 years
Mass left after 20 years = ?
Solution:
First of all we will calculate the number of half lives passed during 20 years.
Number of half lives = time elapsed / half life
Number of half lives = 20 years / 10 years
Number of half lives = 2
At time zero 100 g present.
At first half life = 100 g/2 = 50 g
At 2nd half life = 50 g/2 = 25 g
Thus, after 20 years 25 gram of radioactive material left.
