Question

scandium47 has a half-life of 35s. suppose you have a 45g sample of scadium 47 how much of the sample remains unchanged after 140 seconds

Answer 1

Via the half-life equation we have:

$A_{final}=A_{initial}(\frac{1}{2})^{\frac{t}{h} }$

Where A is the amount initially and final amount after some time has passed, t is the time elapsed, h is the half life time and so:

$A_{final}=45(\frac{1}{2})^\frac{140}{35} = 2.8125g$

Therefore there will be 2.8125 grams left after 140 seconds.