Question

What is the half-life of an isotope if after 2.00 weeks you have 31.25 g remaining from a 250.0 g starting sample size?

Answer 1

starting with 250g ,
after 1 half life 125g,
after 2 62.5g,
after 3 31.25
that is three half lives in two weeks

so one half life must be 14/3 days or 112 hours