02:59:56

A 60.0-g sample of fermium-253 was placed in a sealed vessel 9.0 days ago. Only 7.5 g of this isotope is now left. What is the

half-life of fermium 253?

3.0 days

4.5 days

17.5 days

20.0 days

Half life = 3 days

Explanation:

Given dа ta:

Original amount = 60 g

Amount left after 9 days = 7.5 g

Half life of fermium-253 = ?

Solution:

At time 0 = 60 g

At 1st half life = 60 g/2 = 30 g

At 2nd half life = 30 g / 2 = 15 g

At 3rd half life = 15 g/2 = 7.5 g

Half life = T elapsed / number of half lives

Half life = 9 days / 3

Half life = 3 days