Question

The half-life of a radioactive isotope is three hours. If the initial mass of the isotope were 256 g, the undecayed remaining mass after 18 hours would be
A. `16.0g`
B. `4.0 g`
C. `8.0 g`
D. `12. 0 g`

Answer 1

Correct Answer - B
`t_(1//2)=3`hours
after 18 hours,i.e. after 6 half lines
undecayed remaining mass =`(256)/(2^(6))=(256)/(64)=4g`