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### Unique vs instantaneous rate

Posted: **Sat Mar 02, 2019 9:10 pm**

by **Valeria Viera 1B**

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?

### Re: Unique vs instantaneous rate

Posted: **Sat Mar 02, 2019 9:20 pm**

by **Chem_Mod**

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

### Re: Unique vs instantaneous rate

Posted: **Sun Mar 03, 2019 1:20 am**

by **maldonadojs**

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

### Re: Unique vs instantaneous rate

Posted: **Sun Mar 03, 2019 2:31 am**

by **Katelyn Pham 4E**

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

### Re: Unique vs instantaneous rate

Posted: **Sun Mar 03, 2019 1:09 pm**

by **Milena Aragon 2B**

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).

### Re: Unique vs instantaneous rate

Posted: **Sun Mar 03, 2019 1:49 pm**

by **Sara Flynn 2C**

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

### Re: Unique vs instantaneous rate

Posted: **Sun Mar 03, 2019 11:23 pm**

by **Jacob Bershatski 4C**

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