The half life of radioactive isotope is 3 hour. If the initial mass of isotope were 256 g, the mass of it remaining undecayed after 18 hr is a)12 g b)16 g c)4 g d)8 g

Options

A. 12 g
B. 16 g
C. 4 g
D. 8 g

Answer

c

Explanation

`N = N_(0) ((1)/(2))^(n)` n = number of half lives `= (18)/(3) = 6`
`= 256 ((1)/(2))^(6) = 4 g`