initial reaction rates?

Question

If I am given 2 concentrations (1= 0.075M & 2=0.0188M) how do i find the initial reaction rate? Oh yeah, the time is 54 seconds!

Answer 1

The general equation for this is
C = C0e^-kt
If C0 = 0.075 and C(54) = 0.075e^-54k = 0.0188
-54k = Ln(0.0188/0.075)
k = -(1/54)Ln(0.0188/0.075)
C'(0) = -(1 / 54)[Ln(0.0188 / 0.075)](0.075)

edit:
I meant to do a better job than above, but got called away.
k = -(1/54)Ln(0.0188/0.075)
k = 0.02562280
C'(t) = -0.02562280(0.075)e^-0.02562280t
C'(0) = -0.001921710 M/s