## Chapter 15.12?

Arrhenius Equation: $\ln k = - \frac{E_{a}}{RT} + \ln A$

Sophia Bozone 2G
Posts: 51
Joined: Fri Sep 29, 2017 7:07 am

### Chapter 15.12?

Online it says we will be tested all of chapter 15 excluding 15.9, however 15.12 is quite confusing and contains some equations that I don't recall looking at. What do you think I should know?

Nancy Dinh 2J
Posts: 59
Joined: Fri Sep 29, 2017 7:07 am

### Re: Chapter 15.12?

The equations are basically a mathematical definition of A (collision frequency) and a more complex version of $ln(k)=\frac{E_{a}}{RT} + ln(A)$. I am 99% that you only be using the this equation and not the one that they give you in section 15.12.

As for what you should know from the section, simply know the basics of collision theory. Molecules have to collide with enough energy to overcome the energy barrier Ea. If not, the molecules will simply bounce apart.

If the reaction is endothermic, the activation energy for the forward direction is higher than that for the reverse. Conversely, if the reaction is endothermic, the activation energy for the forward direction is less than that for the reverse. This can be seen in a reaction profile and by the equation $K=\frac{k}{k'}$ where k is the rate constant of the forward reaction and k' is the rate constant of the reverse reaction.

YashDeshmukh1D
Posts: 42
Joined: Fri Sep 29, 2017 7:05 am

### Re: Chapter 15.12?

Collision theory essentially states that molecules (usually in a gaseous phase) will bond if the three requirements are satisfied:
1) whether the molecules are of the right size and traveling at the right speed (this is affected by temperature)
2) whether they have greater than the minimum energy to loosen the reactant's bonds
3) whether they are oriented in the appropriate manner to form bonds (steric requirement)

Justin Lai 1C
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

### Re: Chapter 15.12?

Also know that there in a graph with lnk and 1/T as its axes, the slope will be linear and will equal -Ea/R.

Justin Lai 1C
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

### Re: Chapter 15.12?

I think that the equation is lnk = -Ea/RT + lnA with the negative sign.