CHEMISTRY COMMUNITY

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

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.

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!

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?

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.

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

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')

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

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

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

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.

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

The unique reaction rate depends on the coefficients of the reaction

Thanks!

what is the reaction rate??

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

What is the reaction rate?

These explanations were very helpful! Totally forgot about this !

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

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

Very Helpful!

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

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

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

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.

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

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.

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

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

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!

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

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

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)

so in problems like 7A.3, we just take the unique rate and multiply it by the stoichiometric coefficient to determine the rate of each reactant/product right? just clarifying here, since I'm not 100% confident on the concept of unique rates

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.

Wow this clarified a lot thank you!

What does a unique reaction rate mean again?

Hi!,

A unique reaction rate is the increase or decrease in product concentration that is defined by our stoichiometric coefficient

A unique rate is a rate of appearance/disappearance of any of the species in a reaction divided by its stoichiometric coefficient. A unique rate will be the same for each reactant or product.

The unique rate is the same for all coefficients so you wouldnt balance the equation first.

its unique because the reaction rate is the same for each concentration of products and reactions when it gets multiplied by the stoich coefficient.

Have we seen an example of this in the current 14B classes? I couldn't find an example in the lectures so I'm wondering where I can look for more practice.

Thanks!

a unique reaction rate entails the rat being the same for the concentrations of both the products and the reactants when that reaction rate is multiplied by the coefficient that goes with it. there is no need to specify a species when you are writing a reaction rate.

You need to look at the overall system and then translate the mole content

Will we be tested on the exceptions for the periodic table.

What are some text book problems that can help me with reaction rates?

What will be some indicators in word problems that would suggest that the reactions are unique?