half life is the time taken for
half the mass of an atom to decay,
there
fore if 20g is our original mass and 5g is the remaining or undecayed mass,
then
let us observe in this way
after 1 half life 50% of the original mass disappeared
and 50% is remaining, meaning 10g decayed
and 10 gram is remaining.
After another halflife 50% of the 10g decayed and we are left with
5g.
Therefore two
halflife has elapsed in 8 minutes,
Therefore the half life of this radioactive
sample is 4 minutes or 240seconds
Since know the half life we can find the decay
constant, though not necessary for this question.
·
assume you have a 500 g sample of a radioactive isotope with a half-life of 100 years, find decay constant?
To calculate the decay constant we start
by writing down the equation
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