A half-life of potassium -40 is 1.28X10^9 years. How much of 100.00 g sample will be left after 5.12X10^9 years? .

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Answer 1 · 2018-07-25T05:57:59

The amount left is #=6.25g#

chemwiki.ucdavis.edu

The half -life of # " potassium-40 "# is

#t_(1/2)=1.28*10^9y#

The time is #t=5.12*10^9y#

The initial amount is #m_0=100g#

Half the amount is left after #"one"# half-life

That is

In #1.28*10^9 y#, the amount is #=50g#

As

#t=4*t_(1/2)#

The amount left in #5.12*10^9y# is

#m=100/16=6.25g#