The half-life period of a radioactive element is 140 days. After 560 days, what amount of `1` g of the element will be reduced?

Explanation

Given, `[A]_0 = 1g, t_(1//2) =140 days, t = 650` days
`k = (0.693)/( t_(1//2) ) = (0.693)/(140)`
`therefore t = (2.303)/( k) log"" ([A]_0)/([A])`
`rArr log "" ([A]_0)/( [A]) = (t xx k)/(2.303) = (650 xx 0.693)/( 2.303 xx 140)`
`log"" ([A]_0)/([A]) = 1.397 rArr ([A]_0)/([A]) =" antilog" 1.397`
`([A]_0)/([A]) = 24.94, rArr [A] = (1)/( 24.94)`
`rArr [A] = 0.04" g"`