It is known that the conversion of cyclopropane to propene is a first order
reaction with a rate constant of
K = 6.7x10^-4 s^-1 at 500°C. If the Initial
concentration of cyclopropane was
1.5 M, what is the cyclopropane
concentration after 25 minutes ?

Use first order equation to solve

The cyclopropane  concentration after 25 minutes : [A]=0.549 M

Given

a rate constant k = 6.7x10⁻⁴ /s

Initial  concentration : 1.5 M,

t = 25 min = 1500 s

Required

The final concentration

Solution

For first-order reaction :

[A]=[Ao]e^(-kt)

or

ln[A]=-kt+ln(A0)

Input the value :

ln[A]=-6.7 x 10⁻⁴ x 1500 + ln 1.5

[A]=0.549 M