Chemistry; reaction rate - completion

[General_Sax]

Chemistry; reaction rate -- completion

Homework Statement

A first-order reaction is 17% complete after 30 min. How long after the start of the reaction will the reaction be 80% complete?

Homework Equations

ln[A] = ln[A₀] - kt

The Attempt at a Solution

[A] = 0.83
[A_o] = 1.0
t = 30 min

k = ln(1/0.83) / 30 = 0.006211 min^-1

t = ln(1.0/0.2) / 0.006211 = 259 min


This problem is on a practice exam for my upcoming midterm.

I'm not sure about my choices for [A].

When the reaction is completed the [A] = 0, is that right?

ie, [A] starts at 1.0 -- [A₀] in this problem -- and goes to 0, right?

 

[General_Sax]

oops, when I solved for t I used a different value for [A]

[A] = 0.2