I'm not too sure where to start on this one. I am still confused with the half life concept a little.?
Answer:
Take half each time...
1st half-life... 50.0 grams
2nd half-life... 25.0 grams
3rd half-life... 12.5 grams
Now, remember... the isotope doesn't just disappear. It converts to the less radioactive isotope.
Hope this helps you.
After 1 half life you would have 50 g. After 2 half lives you would have 25 g. After 3 half lives you would have 12.5 g
After the first half-life period, you have 0.5 left. After the second, you have 0.25. After the third, 0.125
100gP-32 x 0.125 = 12.5g P-32
You can also use logarithms to solve related questions like this one.
Af = Ao(0.5)^(x/t)
Af= final amount
Ao = initial amount
x = # of periods ( in this case, 3)
t = period of each half life
Af = 100.0(0.5)^(42.78/14.26)
Or simply Af = 100.0(0.5)^3 since you know 3 half life periods have occured.
Af = 12.5g
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