Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Scholar98 on January 11, 2015, 02:55:01 PM
-
21. A first-order reaction is 45% complete at the end of 35 minutes. What is the length of the half-life of this reaction?
a) 41 min
b) 39 min
c) 30. min
d) 27 min
ne of these
ANS: a) 41 min PAGE: 12.4
How do you solve this. I think you have to use the integrated rate law but I'm not sure how.
-
The integrated rate law gives you concentration as a function of time. Rearrange to give time as a function of conc., and insert the data given to find the rate constant. Then calculate the time for 50% reaction.
-
21. A first-order reaction is 45% complete at the end of 35 minutes. What is the length of the half-life of this reaction?
a) 41 min
b) 39 min
c) 30. min
d) 27 min
ne of these
ANS: a) 41 min PAGE: 12.4
How do you solve this. I think you have to use the integrated rate law but I'm not sure how.
ln(55)-ln(100)/(35)=41
-
ln(55)-ln(100)/(35)=41
That's not correct. Even if you meant {ln(55)-ln(100)}/35, that's not 41 either.
{ln(55)-ln(100)}/35 = -k
Once you know k, you can work out the half-life.
-
.693/0.01708=41
-
That's it.