PDA

View Full Version : Chemistry; reaction rate -- completion


General_Sax
Jan22-10, 01:00 AM
1. The problem statement, all variables and given/known data
A first-order reaction is 17% complete after 30 min. How long after the start of the reaction will the reaction be 80% complete?


2. Relevant equations
ln[A] = ln[A0] - kt


3. The attempt at a solution

[A] = 0.83
[Ao] = 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?
1. The problem statement, all variables and given/known data



2. Relevant equations



3. The attempt at a solution

General_Sax
Jan22-10, 01:01 AM
oops, when I solved for t I used a different value for [A]

[A] = 0.2

General_Sax
Jan23-10, 12:45 PM
bump