試題詳解

29. The decay of strontium-90 follows a first-order process and the rate constant is 0.02406 year⁻¹ . How much of 2 mg sample of strontium-90 remains after 144 years?
(A) 0.250 mg
(B) 0.062 mg
(C) 0.031 mg
(D) 0.125 mg
(E) 0.500 mg