You have 0.1 gram-atom of a radioactive isotope `""_(Z)^(A)` X (half-life = 5 days). How many atoms will decay during the eleventh day ?

Options

A. `1.93 xx 10^(21)`
B. `3.05 xx 10^(22)`
C. `1.31 xx 10^(22)`
D. `4.32 xx 10^(22)`

Answer

C

Explanation

The number of atoms undergoing decay is `N_(0) = 0.1 xx 6.023 xx 10^(23) = 6.023 xx 10^(22)` atoms.
After 11 days, the number of atoms decayed `= N_(0)e^(-lambdat) = 6.023 xx 10^(22) xx e^(-(0.693 xx 11)//5)`