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 data:

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