### Quiz 2 Preparation

Posted:

**Thu Feb 23, 2017 12:21 am**Can someone please explain number 10 from the practice quiz in the course reader

Thanks

Thanks

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=145&t=19822

Page **1** of **1**

Posted: **Thu Feb 23, 2017 12:21 am**

Can someone please explain number 10 from the practice quiz in the course reader

Thanks

Thanks

Posted: **Thu Feb 23, 2017 12:25 am**

You have to use the integrated rate law for second order reactions. After plugging the values in, you will see that the time it takes are different. I used 1/[A]subscript t = 1/[A]0 + kt

Posted: **Thu Feb 23, 2017 12:34 am**

We know its a second order reaction because of the exponent given in the rate law; rate = k[A]^{2}

Using the integrated rate law for second order reactions, we can rearrange the equation and solve for time. Knowing that k is the same constant at both initial concentrations, we can ignore it. This gives t=1/[A]-1/[A]_{0}. When plugging in initial and final concentrations for both 1.0M-->0.50M and 0.50M-->0.25M, we get different times, showing us that half life depends on initial concentration for second order reactions.

Using the integrated rate law for second order reactions, we can rearrange the equation and solve for time. Knowing that k is the same constant at both initial concentrations, we can ignore it. This gives t=1/[A]-1/[A]