First Order Kinetics

Question

A particular reaction is found to be first order. The reactant has an initial concentration of 4.82 M and a rate constant of 0.00610 s−1. Calculate the final concentration of this reactant after 74.5 seconds have passed.

I know the formula is ln[A]f=ln[A]i−kt but I think I am getting my math mixed up somewhere.

Answer 1

Yes, the integrated rate law for a first order reaction is ln[A] = -kt + ln[A]o

[A] = ?

k = 0.00610 s-1

t = 74.5 s

[A]o = 4.82 M

Solving for [A] we have...

ln [A] = -(0.00610)(74.5) + ln 4.82

ln [A] = -0.454 + 1.573

ln [A] = 1.119

[A] = 3.06 M