Question

Two-stroke motor boat engines emit a large amount of partially burned fuel into the water. One of the more common chemicals is phenanthrene . The degradation half-life of phenanthrene is about 7.30 days in clear surface waters. If a motor boat emits 97.0 g of phenanthrene during a short time period (effectively at a single point in time), then how long will it take for 90.0 % of the chemical to degrade away? The units are days

Answer 1

k = 0.693/t_1/2

Then ln(No/N) = kt
No = 100
N = 10
k from above.
Solve for t in days.