試題詳解

72. A certain drug is metabolized in the human body following second-order kinetics, with the rate law given by: Rate= k [D]²
where [D] is the concentration of the drug in mg/L, and k is the rate constant in L·. At
time t=0, the drug concentration in the bloodstream is 20.0 mg/L. After 30.0 min, the
concentration drops to 10.0 mg/L.
How long will it take for the concentration to drop to 5.0 mg/L?
(A) 60.0 min
(B) 45.0 min
(C) 37.5 min
(D) 90.0 min
(E) 120.0 min