Posted by Matthew on Tuesday, December 11, 2012 at 10:57pm.
What is the halflife of a 100.0 g sample of nitrogen16 that decays to 12.5 g of nitrogen16 in 21.6 s? Please help me!!

Chemistry  DrBob222, Tuesday, December 11, 2012 at 11:10pm
ln(No/N) = kt
No = 100g
N = 12.5g
k = solve for this
t = 21.6 sec
Then Substitute k into
k = 0.693/t_{1/2} and solve for t_{1/2}