## Terminology "first-order" [ENDORSED]

$\frac{d[R]}{dt}=-k[R]; \ln [R]=-kt + \ln [R]_{0}; t_{\frac{1}{2}}=\frac{0.693}{k}$

Ashley Davis 1I
Posts: 57
Joined: Fri Sep 29, 2017 7:04 am

### Terminology "first-order"

Do the terms "first-order" and "second-order" only apply to the reaction as a whole and not to the reactants individually? Like if there were two reactants both with coefficients of 1, would we never call the rxn a 2nd-order rxn with two 1st-order reactants?

Britney Alvey 1B
Posts: 31
Joined: Fri Jun 23, 2017 11:39 am

### Re: Terminology "first-order"

You can refer to the order of individual reactants as well as the order of the reaction. The overall order of the reaction is the sum of the orders of each reactant. So, if each reactant has order 1 then the order of the reaction is 2.

Humza_Khan_2J
Posts: 56
Joined: Thu Jul 13, 2017 3:00 am

### Re: Terminology "first-order"

The way you've described it works; a reaction can be first order with respect to its reactants A and B, but in total would be a 2nd order reaction.

Jessica Wakefield 1H
Posts: 58
Joined: Thu Jul 27, 2017 3:00 am

### Re: Terminology "first-order"

they can refer to each reactant separately or to the reaction of the whole. the sum of each of the reactants' orders is the order of the whole reaction.

Manvir2K
Posts: 32
Joined: Fri Sep 29, 2017 7:05 am

### Re: Terminology "first-order"

When commenting on the entire reaction, the overall order should be given-the sum of all the orders of the reactants

204932558
Posts: 23
Joined: Fri Sep 29, 2017 7:05 am

### Re: Terminology "first-order"  [ENDORSED]

The overall order of a reaction is the sum of the order of reactions for each reactants.