Cobalt-57 is radioactive, emitting β -particles. The half-life for this is 270 days. If 100 mg of this is kept in an open container, then what mass (in mg ) of Cobalt-57 will remain after 540 days?

Step-by-step solution

Here, T 1 2 = 270 days. After 540 days, it means two half lives have been completed i.e., n = 2 If N N 0 = 1 2 n ⇒ m m 0 = 1 2 n [ ∵ from Equation. (i)] ⇒ m 100 = 1 4 ⇒ m = 25 mg