The half-life of cobalt-60 is 5.26 years. After 10.52 years, 5 grams of a 20-gram sample will remain. true or false?

True

Explanation:

Given dа ta:

Mass of cobalt = 20 g

Half life = 5.26 years

Mass remain after 10.52 years = 5 g

Solution:

Number of half lives = T elapsed / half life

Number of half lives = 10.52 years / 5.26 years

Number of half lives = 2

At time zero = 20 g

At first half life = 20 g / 2 = 10 g

At second half life = 10 g/2 = 5 g

The given statement is true.