## Rate Law

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

Helen Shi 1J
Posts: 78
Joined: Sat Jul 22, 2017 3:00 am

### Rate Law

So if given a chemical equation, does the coefficient in front of the reactant automatically translate into the exponent in the rate law? So 2NO as a reactant would have a rate law = k[NO]^2?

DianaTrujillo2K
Posts: 40
Joined: Fri Sep 29, 2017 7:04 am

### Re: Rate Law

The order of a rate law is determined experimentally and cannot be determined using the coefficients in the reaction. However, when using the pre-equilibrium approach you use the coefficient as the exponent, but this can only be done when the observed rate law is given and you are trying to determine the rate-determining elementary step of a reaction, like how we did in class today.

Juanyi Tan 2K
Posts: 33
Joined: Fri Sep 29, 2017 7:05 am

### Re: Rate Law

Not really. The rate law is not related to the reaction coefficient. A reaction can be zero order such as rate = k, indicating the rate will not be affected by the concentration of reactant. We determine the rate law through experimental data.

Oscar Valdovinos 1I
Posts: 29
Joined: Fri Sep 29, 2017 7:05 am

### Re: Rate Law

When writing out the rate law equation, the exponents are the orders of the reaction. Therefore, the coefficient doesn't have an effect on the value of the of the exponents.

Angel R Morales Dis1G
Posts: 50
Joined: Sat Jul 22, 2017 3:01 am

### Re: Rate Law

The rate law is determined by r=K[A][B][C], where A B C are reactants. You would determine the overall order through a data table, by finding the exponents of each reactant and adding them together.

Clarissa Molina 1D
Posts: 55
Joined: Fri Sep 29, 2017 7:04 am

### Re: Rate Law

Just for clarification, a catalyst can appear in the rate law but an intermediate cannot?

Matt_Fontila_2L_Chem14B
Posts: 39
Joined: Fri Sep 29, 2017 7:07 am

### Re: Rate Law

Neither catalysts nor intermediates go into the rate law.

Though it does affect the rate at which the reaction proceeds, since a catalyst doesn't count as a reactant or product, it doesn't count in the rate law.