The isotopic composition of rubidium is `Rb^(85):73%` and `Rb^(87):28%Rb^(87)` is weakly radioactive
Channel: Doubtnut
Date: 2020-07-26

The isotopic composition of rubidium is `Rb^(85):73%` and `Rb^(87):28%Rb^(87)` is weakly radioactive and  decay by `beta^(c-)-` emission with a decay constant of `1.1xx10^(-11) ` per year. A sample of the mineral pollucite was found to contain `450g Rb` and `0.72mg ` of `Sr^(87)`. Estimate the age of mineral pollucite stating any assumption made.