3 Questions regarding reaction kinetics- me out.

In summary, Borek explained that the equation -(1/a)*(d[A]/dt)= -(1/b)*(d[B]/dt) = -(1/p)*(d[P]/dt) = -(1/q)*(d[Q]/dt) holds true for all reactions, and that it is possible for the rate of any of the reactants to differ from the rate of the other reactants. He also explained that the order of a reaction does not always equal the coefficients of the reactants.
  • #1
christian0710
409
9
Hi I need some help understanding reaction kinetics, and I’m trying to get an overview, so I’d really appreciate some help. I have 3 individual/quite unrelated questions, if you have time to answer one that would be very much appreciated.

1. In what situations dos the Definition of the reaction rate for a general reaction Hold true?

aA + Bb --> pP+qQ

-(1/a)*(d[A]/dt)= -(1/b)*(d/dt) = -(1/p)*(d[P]/dt) = -(1/q)*(d[Q]/dt)

I would assume this definition only holds true when all the rates are equal, so this does not apply for reactions where the rate of A is different from the rate of B (if this is possible)

2. If the rate of A is slower than the Rate of B, would they then not be comsumed at the same RATE because A would be the limiting factor, the equation -(1/a)*(d[A]/dt)= -(1/b)*(d/dt) holds true for all reactions?

3. Is it true that if the rate law for A + B --> C +D is givn by -d[A]/dt = k[A]^n^m with respect to A, then it might be different with repsect to B? So -d/dt might be different (slower or faster) than -d[A]/dt, so the -d[A]/dt=-d/dt = k[A]^n*^m only holds true for elementary reactions, while for complex reactions the rate law for -d[A]/dt could be equal to k[A] raised to a first order while -d/dt could be equalt to k[A]^2^1 (something different?)
 
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  • #2
christian0710 said:
I would assume this definition only holds true when all the rates are equal, so this does not apply for reactions where the rate of A is different from the rate of B (if this is possible)

It is not possible. I already told you somewhere else that we use stoichiometric coefficients to make sure rates of the reaction for all substances involved are identical.
 
  • #3
Hi borek, yes i was a bit confused on what question you were answering but now it seems more clear to me: What you are saying is that No matte what reaction we have (Zero order, first order, second order, complex) the equation -(1/a)*(d[A]/dt)= -(1/b)*(d/dt) = -(1/p)*(d[P]/dt) = -(1/q)*(d[Q]/dt) is true? and in some cases the rate of any of the reactants might display the following relationship = k[A]^m^n (for complex reactions) and in elementary reactions the orders of the reaction equals the koefficients of the reactants?

If this is a correct understanding, I'm really happy :)
 
  • #4
Ohh yes an just to make sure it's 100% clear for me:

If -(1/a)*d[A]/dt)=k[A]^m^n

Then This must also be true

-(1/b)*(d/dt)=k[A]^m^n

:)
 
  • #5
christian0710 said:
No matte what reaction we have (Zero order, first order, second order, complex) the equation -(1/a)*(d[A]/dt)= -(1/b)*(d/dt) = -(1/p)*(d[P]/dt) = -(1/q)*(d[Q]/dt) is true?


and in some cases the rate of any of the reactants might display the following relationship = k[A]^m^n (for complex reactions) and in elementary reactions the orders of the reaction equals the koefficients of the reactants?


christian0710 said:
If -(1/a)*d[A]/dt)=k[A]^m^n

Then This must also be true

-(1/b)*(d/dt)=k[A]^m^n


Yes, yes, yes & yes.
 
  • #6
Thank you very much Borek - Now I'm really happy :D
 

1. What is reaction kinetics?

Reaction kinetics is the study of the rate at which chemical reactions occur and the factors that influence this rate, such as temperature, concentration, and catalysts.

2. Why is reaction kinetics important?

Reaction kinetics is important because it helps us understand and control chemical reactions in various fields, including pharmaceuticals, materials science, and environmental science. It also allows us to optimize reaction conditions for maximum efficiency and safety.

3. How do you determine the rate of a reaction?

The rate of a reaction is typically determined by measuring the change in concentration of a reactant or product over time. This can be done experimentally by monitoring the reaction using techniques such as spectrophotometry or titration, or by analyzing the reaction using mathematical models.

4. What factors affect the rate of a reaction?

The rate of a reaction can be affected by several factors, including temperature, concentration of reactants, presence of a catalyst, surface area of reactants, and the nature of the reactants and products.

5. What is a reaction mechanism?

A reaction mechanism is a series of individual steps that make up a chemical reaction. It explains the sequence of events that occur during the reaction and the intermediates and products formed at each step. Understanding the reaction mechanism is essential for understanding and predicting the behavior of a chemical reaction.

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