## Units for Reaction Rate and the Rate Constant

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

Hector_Gutierrez 1J
Posts: 23
Joined: Wed Sep 21, 2016 2:58 pm

### Units for Reaction Rate and the Rate Constant

In general, what are the units for the reaction rate and the rate constant? I mean individually of course as the they are different values.

Anna_Kim_2E
Posts: 31
Joined: Wed Sep 21, 2016 2:56 pm

### Re: Units for Reaction Rate and the Rate Constant

The units of rate constant is varies for the different depending on the order of reaction.

Janice Kim 3I
Posts: 33
Joined: Wed Sep 21, 2016 2:56 pm

### Re: Units for Reaction Rate and the Rate Constant

The reaction rate units is usually in the form mol L^-1 s^-1 (the time unit can vary - s, min, hr, etc). The rate constant depends on the order of the reaction. For example, if first order, the rate constant will be s^-1. You can find this by dividing the units of the reaction rate by the unit of the right hand side. In this case, it is first order so the right hand side unit will be mol L^-1.

Molika Soben_3J
Posts: 27
Joined: Wed Sep 21, 2016 3:00 pm

### Re: Units for Reaction Rate and the Rate Constant

The unit for the reaction rate is generally mol*L^-1*s^-1 or M*s^-1 for which M is mol*L-1. As for the units for the rate constant, it depends on the order of the reaction. For zero-order reactions, the units are mol*L^-1*s^-1 or M*s^-1 like the reaction rate. For first-order reactions, the units are s^-1. And for second-order reactions, the units are L*mol^-1*s^-1. You can check this by dividing the units of the reaction rate with the units you have on the other side where for instance, as A->products, the reaction rate=k[A]^1 which would be a first-order reaction. Since [A] is measured in mol*L^-1, you can divide those units to the reaction rate units to be left with s^-1 as the units of k. I believe that in the homework problem it asked us to find the units for the rate constant as well. It is problem 15.9?