### K'

Posted:

**Sun Mar 04, 2018 12:50 am**Is the slope the only way to determine K'?

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=146&t=28828

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Posted: **Sun Mar 04, 2018 12:50 am**

Is the slope the only way to determine K'?

Posted: **Sun Mar 04, 2018 4:27 am**

You can also use the formulas given in the equations sheet. Just make sure you understand the formulas and which order reaction to use them for.

Posted: **Sun Mar 04, 2018 12:35 pm**

We use k' for pseudo order rate laws and it denotes the rate constant at the specific conditions you are studying. For psuedo order rate laws, you generally obtain k' from the slope of the linear plots you are looking it. You can't use the formulas on the sheet because you're finding k at altered conditions.

Posted: **Mon Mar 05, 2018 4:46 pm**

Could someone explain what methods you would use to find k' in a pseudo reaction?

Posted: **Mon Mar 05, 2018 4:56 pm**

To find K' in a pseudo reaction, like a second order reaction, you would solve for k without changing the concentration of one of the reactants that is first order. That reactant must be in so much surplus that its concentration would not change through the reaction. Thus, the reaction becomes a first order reaction for the other reactant, and you can solve for k' as such.

We set k such that k = k'[A], where A is the reactant in surplus. After solving for k', you can plug it in to the first order reaction to yield Rate = k'[B]

We set k such that k = k'[A], where A is the reactant in surplus. After solving for k', you can plug it in to the first order reaction to yield Rate = k'[B]

Posted: **Tue Mar 06, 2018 9:03 am**

There is also an equation if you are solving for k' for rate = k [A] [C], k = k'/[initial B]m [initial C]l[/b] when [B] and [C] are in surplus,

Posted: **Tue Mar 06, 2018 9:06 am**

Sorry, the equation is k = k'/([B initial]m [C initial]l)

Posted: **Tue Mar 06, 2018 11:42 am**

K' is simply the substitution during a pseudo reaction that sets one of the reactants at a high concentration so that we can only focus on the changing aspect of one reactant. It makes it simpler to analyze the changing rate of the reaction when only focusing on one reactant.