A radioactive element of mass 20.0g was isolated and stored. It was discovered after 40days that 2.5g of the element remained undecayed. Calculate the half life of the element.

Half life = 13.3 days

Explanation:

Given dа ta:

Mass of element = 20.0 g

After 40 days a mass left = 2.5 g

Half life of element = ?

Solution:

At time zero = 20.0 g

At first half life = 20.0 g/2 = 10.0 g

At second half life = 10.0/2 = 5.0 g

At third half life = 5.0 g / 2 = 2.5 g

Half life:

Half life = T elapsed / number of half lives

Half life = 40 days / 3

Half life = 13.3 days