## When B and C is significantly larger than A

$aR \to bP, Rate = -\frac{1}{a} \frac{d[R]}{dt} = \frac{1}{b}\frac{d[P]}{dt}$

Julianne Seog 3K
Posts: 24
Joined: Wed Sep 21, 2016 2:58 pm

### When B and C is significantly larger than A

In the course reader, it says if the concentration of B and C is significantly larger than A then the reaction rate depends only on A. How much is "significantly larger" so that this rule can apply?

Johnson Thai 1L
Posts: 19
Joined: Wed Sep 21, 2016 2:59 pm

### Re: When B and C is significantly larger than A

I believe it is just "significantly large" enough so that the concentrations of B and C remain constant when A is being used up. This way, as stated in the Course Reader, the reaction rate depends on just concentration of A.

Cherry_Deng_1K
Posts: 12
Joined: Wed Sep 21, 2016 2:55 pm

### Re: When B and C is significantly larger than A

Also, I am pretty sure a question will tell you that the concentrations of B and C are significantly larger than A. You will probably not know to write a pseudo-first-order rate law (or other order depending on the reaction) otherwise.

ChristinaRoble3J
Posts: 14
Joined: Fri Jul 15, 2016 3:00 am

### Re: When B and C is significantly larger than A

I also don't understand this in my opinion "significantly large" is very subjective, so I am also confused as to how we know if one or two of the reactants are in "large excess" in comparison to another. I hope lavelle goes over this.