## Unique vs instantaneous rate

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

Valeria Viera 1B
Posts: 60
Joined: Fri Apr 06, 2018 11:05 am

### Unique vs instantaneous rate

In Friday’s lecture, professor Lavelle explain the difference between the unique rate and the instantaneous rate but I don’t think I understood
Could anyone explain?

Chem_Mod
Posts: 19140
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 820 times

### Re: Unique vs instantaneous rate

AVERAGE RATE = (CONC(t2) − CONC(t1))/(t2 −t1) = ∆CONC/∆t

INSTANTANEOUS RATE = −(d[R])/dt
OR
INSTANTANEOUS RATE = (d[P])/dt

AVERAGE & INSTANTANEOUS RATES CAN BE DIFFERERENT FOR THE INDIVIDUAL R & P.
THINK OF THEM AS THE EXPERIMENTALLY MEASURED RATES (COLLECTED DATA) OVER LONG TIME INTERVALS (∆) OR SHORT TIME INTERVALS (d).

UNLIKE THE UNIQUE RATE WHICH IS CALCULATED AND IS THE SAME FOR ALL R & P IN THAT ‘UNIQUE’ REACTION WHERE:

UNIQUE RATE = −1/a (d[A])/dt = 1/b (d[B])/dt = 1/c (d[C])/dt

IN THE REACTION: a A ---> b B + c C

Posts: 57
Joined: Fri Sep 28, 2018 12:27 am

### Re: Unique vs instantaneous rate

The unique rate just takes coefficients into account and you multiply them to the concentration (the ones you use in an instantaneous rate).

Katelyn Pham 4E
Posts: 30
Joined: Fri Sep 28, 2018 12:21 am

### Re: Unique vs instantaneous rate

The unique rate only applies to a given reaction such as a A ---> b B + c C because it has coefficients, unlike instantaneous rate.

Milena Aragon 2B
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

### Re: Unique vs instantaneous rate

The unique rate actually makes it so that you can refer to the rate without having to indicate the species it's referring to since it is the same throughout the reaction (this is because the coefficient was divided from it and all you're left with is the rate for 1 mol of that reaction).

Sara Flynn 2C
Posts: 60
Joined: Fri Sep 28, 2018 12:23 am

### Re: Unique vs instantaneous rate

When calculating the instantaneous rates you are finding it for a specific species and the unique rate takes into account the stoichiometric coefficient of the equation and so it makes all the unique rates for each species that same

Jacob Bershatski 4C
Posts: 30
Joined: Fri Sep 28, 2018 12:21 am

### Re: Unique vs instantaneous rate

The instantaneous rate is equal to the limit of the average rate as delta(t) approaches 0.

### Who is online

Users browsing this forum: No registered users and 1 guest