Conversion of cyclopropane to propene

[geffman1]

Homework Statement

We examine the conversion of cyclopropane to propene, a first order process. If we begin with 0.0200 M cyclopropane and find that after 168 s the concentration of propene is 0.00286 M, what is the rate constant, k, at this temperature?



i used the forumula ln[A]/=-kt
=(ln 0.00286/0.02)/168=-k
therefore k=0.0116
however answer is 9.19 x 10-4/s

anyhelp would be good.
thanks

 

[tiny-tim]

We examine the conversion of cyclopropane to propene, a first order process. If we begin with 0.0200 M cyclopropane and find that after 168 s the concentration of propene is 0.00286 M, what is the rate constant, k, at this temperature?

Hi geffman1!

Aren't you using the formula for 0.0200 M cyclopropane and 0.00286 M cyclopropane?

 

[geffman1]

hey, umm yep? I am confused

 

[tiny-tim]

hey, umm yep? I am confused

Perhaps I've misunderstood your equation, but the question gives you the concentration of different compounds, and I think you've used an equation that asumes they're the same compound.