Zero Order

[Kiran Marla]

How do I know when to use A in the the equation k=Ae^(Ea/RT). Also, how do I know when there is no orientation needed?

[Rob Tsai 2F]

I don't think it's a question of when to use A in the Arrhenius Equation, if I'm understanding your meaning correctly. You always use every part of the equation as it is written out. In terms of how to use it, I'm fairly certain that some problems will list it as a given of the problem, so you won't have to calculate it; or you might get a problem where you need to solve for A using the other parts of the equation. Though, I probably recommend going through some textbook problems to make sure because I'm not 100% on that.

No orientation is need when there is no angle of dependence that a molecule needs to be oriented at to collide at to form a new compound. A would be equal to 1. This happens when the molecule has a spherical electron density, meaning that the area in which an electron could be at a given time takes on a spherical shape. In this case, there would be no angle of dependence as a molecule could to the molecule with spherical electron density anywhere and the bonding could take place. Hope this helps, and correct me anywhere I'm wrong please!

[Michelle Jeong 1B]

You will use A if it is given. Most times you are conparing the rate contants at different activation energies or temperatures so making the ratio of one equation over the other equation will cancel out A.

[jennaj3k]

A will be given if we need it. The only problems I've seen where we calculate A is where we're given pretty much everything else. If there is no "angle of dependence" that a molecule needs to collide w/ another molecule, then A=1. All other cases we've been given A.

[Skylar Lo 2C]

A will be provided when needed otherwise it is generally unused.