## Question About the 1st Order REaction Rate Law

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

Rhiannon Imbeah 2I
Posts: 30
Joined: Fri Sep 25, 2015 3:00 am

### Question About the 1st Order REaction Rate Law

Will we ever have to use this rate law to calculate the product concentration or is it only used for reactant concentrations?

Khang_Tran_1O
Posts: 26
Joined: Fri Jul 22, 2016 3:00 am
Been upvoted: 1 time

### Re: Question About the 1st Order REaction Rate Law

I think you're talking about the differential rate laws because for the first order rate law, you just have to work with initial and final concentration, one of which is usually given to you. But for the differential rate laws, which I think the question is referring to, then yes you have to always use reactant concentrations.

Jessica Pak 2F
Posts: 10
Joined: Wed Sep 21, 2016 2:55 pm

### Re: Question About the 1st Order REaction Rate Law

I think that reactant concentrations will always be used unless the reverse reaction is used! (so technically the products are now the reactants)