## units of rates and rate constants

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

Saachi_Kotia_4E
Posts: 68
Joined: Fri Sep 28, 2018 12:23 am

### units of rates and rate constants

what are the basic units for rates and rate constants? are they different for different orders?

Chem_Mod
Posts: 18400
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 435 times

### Re: units of rates and rate constants

Rate of a reaction is generally monitoring the change in concentration over time, thus M/s. For different order reaction, yes rate constants will vary in units, but rate will not.

Kirsty Star 2H
Posts: 48
Joined: Fri Sep 28, 2018 12:24 am

### Re: units of rates and rate constants

For 0 order reactions, the units for k are M/s, for 1st order reactions, the units for k are 1/s, and for 2nd order reactions the units for k are 1/M*s. With M being molarity or concentration

Kavvya Gupta 1H
Posts: 35
Joined: Fri Sep 28, 2018 12:21 am

### Re: units of rates and rate constants

for 0 order reaction, k = mol/Ls. For 1st order, k = 1/s. For 2nd order, k = L/(mol s). Overall the units for a reaction should be mol/Ls

lindsey_ammann_4E
Posts: 61
Joined: Fri Sep 28, 2018 12:26 am

### Re: units of rates and rate constants

The above responses are correct. You can think of dividing the units by moles as you move up to the next order.