### Unique Reaction Rates

Posted:

**Wed Feb 28, 2018 5:21 pm**Such as in 15.3C and 15.5, I just wanted some clarification on what "unique" rate of a reaction means.

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=145&t=28677

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Posted: **Wed Feb 28, 2018 5:21 pm**

Such as in 15.3C and 15.5, I just wanted some clarification on what "unique" rate of a reaction means.

Posted: **Wed Feb 28, 2018 5:52 pm**

It's a unique reaction rate because it is the same for all concentrations of reactants and products when it is multiplied by their stoichiometric coefficient. The species doesn't need to be specified when writing a unique rate.

Posted: **Thu Mar 01, 2018 7:38 pm**

I will discuss this in class tomorrow.

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

Hopefully this clarifies.

Stay warm and see you in class!

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

Hopefully this clarifies.

Stay warm and see you in class!

Posted: **Sat Mar 03, 2018 12:41 pm**

Does this mean that even if all the stoichiometric coefficients were different, because of the concentrations of each species then all rates would be the same? And does unique rate refer to the equality of all rates or of one species only?

Posted: **Sat Mar 03, 2018 9:19 pm**

If all of the stoichiometric coefficients were different, the unique rate can still be the same using any of them to calculate it because we are multiplying the (change in concentration/change in time) by 1/coefficient. This therefore allows us to calculate the unique rate using any of the species in the reaction. The unique rate refers to the one rate calculated using one of the species. The equality formula is just to show that it does not matter which one you choose as long as you multiple by 1/coefficient and negate the equation if it is a reactant.

Posted: **Sun Mar 04, 2018 9:55 pm**

I'm still confused as to how we know when to use the instantaneous rate and the unique rates?

Posted: **Sun Mar 04, 2018 10:35 pm**

I think instantaneous rate is the general but more accurate measure of the rate of change of concentration, and unique rate is like the instantaneous rate of individual species. (so the name 'unique')

Posted: **Tue Mar 06, 2018 1:02 pm**

Anika_Patel_1G wrote:If all of the stoichiometric coefficients were different, the unique rate can still be the same using any of them to calculate it because we are multiplying the (change in concentration/change in time) by 1/coefficient. This therefore allows us to calculate the unique rate using any of the species in the reaction. The unique rate refers to the one rate calculated using one of the species. The equality formula is just to show that it does not matter which one you choose as long as you multiple by 1/coefficient and negate the equation if it is a reactant.

Thank you so much! your response is very helpful

Posted: **Wed Mar 07, 2018 11:38 am**

I'm pretty sure the unique rate is the same for every reactant, so you just wouldn't take the stoichiometric coefficients into account.

Posted: **Sun Mar 11, 2018 1:32 pm**

I will say the rate of a chemical reaction is the change in concentration over the change in time and is a metric of the "speed" at which a chemical reactions occurs.

And Unique rate is the rate occurs per unit of each molecules

And Unique rate is the rate occurs per unit of each molecules

Posted: **Mon Mar 12, 2018 7:30 pm**

A unique rate is the same for all of the materials in the reaction (products and reactants) because it multiplies the change in substance by one over its coefficient.

Posted: **Tue Mar 13, 2018 8:29 pm**

It's a unique reaction rate because its the same for all concentrations of reactants and products when multiplied by their stoichiometric coefficient.

Posted: **Tue Mar 13, 2018 11:08 pm**

The unique reaction rate depends on the coefficients of the reaction

Posted: **Fri Mar 16, 2018 8:47 pm**

Thanks!

Posted: **Fri Apr 27, 2018 3:28 pm**

what is the reaction rate??

Posted: **Sun Apr 29, 2018 4:40 pm**

The reaction rate is the measure of change in concentration of the reactants or the change in concentration of the products per unit time.

Posted: **Tue Oct 23, 2018 1:15 pm**

What is the reaction rate?

Posted: **Fri Oct 26, 2018 9:51 am**

These explanations were very helpful! Totally forgot about this !

Posted: **Thu Nov 08, 2018 3:39 pm**

Chem_Mod wrote:I will discuss this in class tomorrow.

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

Hopefully this clarifies.

Stay warm and see you in class!

Thank you for the information

Posted: **Thu Nov 15, 2018 10:54 am**

Unique rate depends on the stoichiometric coefficient, but stays the same for all products and reactants in the reaction.

Posted: **Sun Nov 25, 2018 3:18 pm**

Very Helpful!

Posted: **Mon Nov 26, 2018 12:12 am**

The unique rate has to do with the stoichiometric coefficients because it stays the same (proportionality)

Posted: **Mon Nov 26, 2018 12:46 am**

The unique rate stays constant for all reactants and depends on coefficients of the reaction.

Posted: **Sun Dec 02, 2018 1:02 pm**

The unique rate depends on the stoichiometric coefficient & stays the same for all products and reactants

Posted: **Sat Mar 09, 2019 7:10 pm**

The unique reaction rate is defined as the rate of the increase in product concentration or the rate in decrease of product concentration divided by the stoichiometric coefficient.

Posted: **Fri Mar 15, 2019 10:51 pm**

When do we use the instantaneous rate versus the unique rates?

Posted: **Sat Mar 16, 2019 1:21 pm**

riddhiduggal wrote:When do we use the instantaneous rate versus the unique rates?

I am also still really confused on this. If I find out, I’ll let you know.

Posted: **Sat Mar 16, 2019 11:13 pm**

what is the difference between the instantaneous rate and the unique rate law??

Posted: **Sun Oct 13, 2019 11:20 am**

In what situations and types of problems will we have to use instanteous reaction rates?

Posted: **Sun Oct 27, 2019 10:06 pm**

Thank you for clarifying!

Chem_Mod wrote:I will discuss this in class tomorrow.

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

Hopefully this clarifies.

Stay warm and see you in class!

Posted: **Mon Oct 28, 2019 11:51 am**

Peter Dis1G wrote:I think instantaneous rate is the general but more accurate measure of the rate of change of concentration, and unique rate is like the instantaneous rate of individual species. (so the name 'unique')

unique rate is is the same for all reactants because of its coefficients

Posted: **Mon Nov 04, 2019 3:41 pm**

Combustion is also unique in that it will always have some reactants and some products that remain the same. (CO2, H2O)

Posted: **Mon Nov 11, 2019 7:31 pm**

Thank you

Mitchell Koss 4G wrote:Combustion is also unique in that it will always have some reactants and some products that remain the same. (CO2, H2O)