20=A(.5)^-28
A=20(2)^28
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20*2^28=
The half-life of the Nobelium isotope No^257 is about 23 seconds. 644 seconds (or 28 half-life periods) after the isotope was released there were 20 grams remaining. The number of grans of No^257 after h half life periods is M= 20 * (1/2)^h where h = 0 corresponds to 644 seconds after the isotope was released. How much No^257 initially released? Answer in units of g.
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