Question

A compound decomposes according to the first order rate law with a half life period of 30 min. What will be the fraction of the remaining compound after 120 min?

(a) 0.625

(b) 0.0625

(c) 0.25

(d) 0.025

This question was posed to me during an online exam.

This interesting question is from Integrated Rate Equation and Half Lives topic in section Reaction Dynamics of Engineering Chemistry I

Answer 1

Correct option is (b) 0.0625

Explanation: k = 0.693/t1/2

  K = (2.303/t) log ([R0]/[Rt]).