The half life for a first order reaction is 45 min. What is the rate constant in units of s^-1

Question

Quizplus · Accepted Answer

The half-life for a first-order reaction is given by the equation: t1/2 = ln(2)/k, where k is the rate constant.
Plugging in the given half-life of 45 min:
45 min = ln(2)/k
Rearranging to solve for k:
k = ln(2)/45 min = 2.6 x 10^-4 s^-1
Therefore, the rate constant in units of s^-1 is 2.6 x 10^-4 s^-1. Since none of the answer choices match this unit, we need to convert to the units given in the answer choices. 
Multiplying by 60 s/min, we get:
k = 0.0156 s^-1
The answer choice closest to this value is (A) 0.015 s^-1, but it is slightly lower. The true answer is actually closer to (B) 65 s^-1, but still not an exact match. Answer choice (C) 2.6 x 10^-4 s^-1 is the only one that matches the given units, and is the correct choice.

The Half Life for a First Order Reaction Is 45