Calculate the half life

Question

A 1.00 g sample of samarium emits alpha particles at a rate of 120 particles/s. The
responsible isotope is 147 Sm, whose natural abundance in bulk samarium is 15%. Calculate
the half life.

Answer 1

Hi Sapphron!

 

I'll think about it some more, but -- at first look -- I do not think there is enough information here to completely answer this question.  We would have to either know the decay constant for Sm 147, or have some time information here that allows us to calculate it (such as either the initial decay rate or the current number of undecayed particles).  Without that, both half-life and the decay constant are unknown, and there is only one independent equation connecting them.

 

Are you allowed to look up -- or are you given a value for -- the decay constant for Sm 147?  I'll think about this some more, or perhaps another tutor has a different idea.  Sorry for the lack of help right away!