Question

The half-life for radioactive decay of an element X is 140 days. Complete the following flow chart showing decay of 1 g of X

Answer 1

1g \(\overset{140\,days}\longrightarrow\) \(^1_2g\) \(\overset{140\,days}\longrightarrow\) \(^1_4g\) \(\overset{140\,days}\longrightarrow\) \(^1_8g\) \(\overset{140\,days}\longrightarrow\) \(^1_{16}g\) 

Shortcut method: 

Amount of the element X left after n half-lives is given as [X] = \(\frac{[x]_0}{2^n}\)

e.g. \(\frac{1}{2^4}\)g = \(\frac{1}{16}g\)