Question

Pleaseeeeeee hlepThe half-life of cobalt-60 is 5.26 years. After 10.52 years, 5 grams of a 20-gram sample will remain.

Answer 1

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

Explanation:

Mass of cobalt = 20 g  

Half-life = 5.26 years  

Mass remains after 10.52 years = 5 g  

This can be solved by using given below formula, $m(t)=m_{o}\left(\frac{1}{2}\right)^{\frac{l}{5.26}}$

$m_{0}$ = initial mass  

t = number of years from when the mass was m_0  

m(t) = remaining mass after t years  

Number of half-lives = $\frac{\text { Time elapsed }}{\text { Half -life }}$

Number of half-lives = $\frac{10.52 \text { years }}{5.26 \text { years }}$

Number of half-lives = 2  

At time zero = 20 g  

At first half-life = $\frac{20\ g}{2}$  = 10 g  

At second half life = $\frac{10\g}{2}$ = 5 g  

The given statement is true.