Q. In a first-order reaction A → B, if k is rate constant and initial concentration of the reactant A is 0.5 M, then the half-life is
A) log 2/k
B) log 2/(k√0.5)
C) ln 2/k
D) 0.693/(0.5k)
Explanation
[Solution from source] For a first-order reaction t½ = ln 2/k = 0.693/k, independent of the initial concentration. log 2/k uses the base-10 log, and 0.693/(0.5k) wrongly brings in the 0.5 M concentration. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.