Chemistry
posted by Matthew .
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!!

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}