Question

The half-life of Co-59 is 35 days. How much of a 610.0-gram sample will remain after 140 days?

Answer 1

Answer:

Amount left after 140 days is 38.125 g.

Explanation:

Given data:

Half life of Co-59 = 35 days

Total mass of sample = 610.0 g

Sample remain after 140 days = ?

Solution:

Number of half lives passes during 140 days:

Number of half lives  = T elapsed / Half lives

Number of half lives  = 140 days / 35 days

Number of half lives  = 4

Amount left:

At time zero = 610 g

At first half life = 610 g/2 = 305 g

At second half life = 305 g/2 = 152.5 g

At 3rd half life = 152.5 g/2 = 76.25 g

At 4th half life = 76.25 g /2 =38.125 g

Amount left after 140 days is 38.125 g.