Questions tagged [kinetics]
The study of rates and steps in mechanisms of chemical processes.
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questions
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20 views
How do we solve this chemical engineering problem based on chemical kinetics? [closed]
Please solve the question in the image, I have an assignment to submit and I can't solve this last question.
2
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0answers
32 views
Is the effect of hydroperoxyl radicals significant in the oxidation of organic compounds in the Fenton reaction? Why or why not?
In the Fenton reaction, a ferrous catalyst and hydrogen peroxide are used to generate hydroxyl radicals which in turn oxidise organic compounds. The reaction is commonly seen in the treatment of ...
0
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0answers
28 views
Steric hindrance during collisions [closed]
How is steric hindrance qualitative (relating to, measuring, or measured by the quality of something rather than its quantity) as whole chemistry runs on chemical kinetics and thermodynamics?
5
votes
1answer
113 views
Nitrogen dioxide fluorescence quenching and lifetime
Nitrogen dioxide fluorescence quenching:
$$
\begin{align}
\ce{NO2 + h\nu &->[$\varphi_\mathrm{Ia}$] NO2^{\ast}}\tag{I}\\
\ce{NO2^{\ast} &->[$k_2$] NO2 + h\nu'}\tag{II}\\
\ce{NO2^{\ast} +...
2
votes
1answer
41 views
Where does the RT term come from in the derivation for the activation enthalpy from the Eyring equation?
It is easy to show an Arrhenius-like equation from the Eyring equation, but if you do this, you get that the activation energy is about equal to the activation enthalpy. However, the real ...
0
votes
1answer
43 views
Rate law of reactions, what about the proportions? [closed]
Consider the reaction
$$\ce{A + B + C -> D + E}$$
and $\mathrm{rate} = k[\ce{A}][\ce{B}]^2.$ My book said if we double the amount of $\ce{A},$ then the reaction rate will double.
I understand ...
0
votes
0answers
24 views
Mass Transport and Ion Transport - Li-ion Batteries
I am new to the field and trying to grasp the theories/ physical phenomena behind the Li-ion batteries. I came across two phenomenons 'Mass transport' and 'Ion transport'.
As I understood Mass ...
2
votes
0answers
48 views
Can a catalyst appear in the rate equation? [duplicate]
According to Wikipedia:
Chemical reactions occur faster in the presence of a catalyst because the catalyst provides an alternative reaction pathway with a lower activation energy than the non-...
0
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0answers
17 views
Are SN1 reactions pseudo unimolecular first order reactions?
I believe the the Solvent (present in excess) helps in ionisation of R-X to carbocation in Rate Determining step so shouldn't the Rate Determining step be a pseudo-unimolecular reaction as 2 molecules ...
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0answers
32 views
How to apply rate law in equilibrium reactions
How do I find out how long it will take to attain equilibrium, given equilibrium constant and rate of forward reaction?
I know that equilibrium constant is also rate of forward reaction/rate of ...
2
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0answers
56 views
The pH of a drop of water containing ammonia
Presented with the following equations: What would the $\mathrm{pH}$ of a drop of water be, while in equilibrium with $\ce{NH3(g)}$ at a concentration of $\pu{150 ppb}$?
$$\ce{NH3_{(g)} + H2O_{(l)} &...
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0answers
21 views
Kinetic Constant Ratio and Equilibrium Constant (Single Product Bi-molecular Reaction)
For an elementary bi-molecular reaction where two (dilute) reactants form a single product in water
$A+B{\rightleftharpoons}C$
I have read that the correct way to express the equilibrium constant is ...
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0answers
25 views
Is it ideal to use a Zahn cup to measure the viscosity of honey?
I am a high school student, and I'm looking for the ideal way to measure honey's viscosity. unfortunately, we do not have a viscometer so I cannot use that but I made some research and the most ...
2
votes
0answers
49 views
What is the recipe for the Belousov-Zhabotinsky reaction for correct simulation with the Oregonator model? [closed]
For a school project I'm trying to model the Oregonator and perform some experiments with the Belousov-Zhabotinsky reaction. Like predicting the reaction and the swings in concentrations. For that it ...
1
vote
0answers
32 views
Production rate of parallel reactions
The degradation of hydrogen peroxide in water $\ce{(2 H2O2 (aq) ā 2 H2O +O2 (g))}$ can be catalyzed by $\ce{Br-}$ and $\ce{H3O+}$. Derive an expression for the production rate for the following ...
2
votes
2answers
80 views
How to calculate the half time of a unimolecular reaction given the Arrhenius coefficient and the activation energy?
Consider the following unimolecular reaction:
$$\ce{H2O2 + M -> OH + OH + M}$$
The high pressure limit unimolecular rate coefficient for this reaction is $k_\mathrm{uni} = A\cdot \mathrm{e}^{...
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votes
0answers
23 views
Kinetics and molecularity vs order [duplicate]
In the field of Chemical Kinetics, terms like Molecularity and Order Of Reaction are often used. I am a bit confused between these two terms.
Can someone explain to me about these two terms and their ...
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1answer
72 views
Find order of reaction 2A ā B + C
Derive the integrated rate expression for a reaction of type:
$$\ce{2A -> B + C}$$
I first need to determine the order of the reaction in order to find integrated rate law of that particular ...
3
votes
2answers
73 views
How do we know a reaction is in equilibrium?
In teaching secondary science equilibrium, how can we actually show there is a backwards reaction occurring during equilibrium rather than no reaction. A lot of equilibrium experiments involve ...
4
votes
1answer
43 views
What is the rate expression for decomposition of $\ce{H2O2}$ in the presence of a catalyst?
What is the rate expression for decomposition of $\ce{H2O2}$ in the presence of a catalyst?
As far as I know for catalase, it is like this: $$\ce{Rate = k[H2O2][Catalase]}$$
I don't know what it is ...
1
vote
1answer
39 views
Does lower activation energy definitely mean higher rate?
Does lower activation energy definitely mean higher rate? For example the decomposition of $\ce{H2O2}$. Can we say it has the highest rate with the catalyst making the reaction's activation energy the ...
2
votes
3answers
74 views
How does the derivative of concentration make sense?
First of all, I would like to make clear that I don't know very much about chemistry, and I'm not very sure this is the right place on Stack Exchange for this question, so please let me know if it ...
5
votes
4answers
229 views
Why do so many biochemical reactions require enzymes?
Studying biochemistry as part of the Great Courses, I am struck that all 10 steps in glycolysis require an enzyme.
Iād have thought that evolution would have selected for a āsimplerā pathway with ...
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votes
1answer
38 views
Conversion and reactor time [closed]
Lets say it takes my batch reactor 3 hours for 35% conversion.
If I wanted to find how long it would take for 15% then,
35-15 = 20,
then 3 hours/0.20 = 0.15 hours for 15% conversion.
I am not too ...
1
vote
0answers
36 views
How to model the Belousov-Zhabotinsky (BZ) (in Maple) [closed]
I need to model the Belousov-Zhabotinsky reaction (or a different oscillating one). I found out about the Oregonator and the Brusselator reaction and now I want to model them in Maple (or similar ...
5
votes
1answer
54 views
Ammonia decomposition on platinum surface
I was given a problem I have to solve, unfortunately I cant wrap my head about it. I've searched the page for answers but they doesnt seem to fulfill my needs, so i'm asking for little guidance.
The ...
2
votes
1answer
46 views
what is the physical significance of āH=āU for a chemical reaction?
In case of few chemical reactions $\Delta n=0$,so according to the equation $\Delta H= \Delta U+\Delta nRT$ change in enthalpy equals change in internal energy. But what does this in essence actually ...
0
votes
1answer
45 views
What you understand by “Order of reaction”? [closed]
When studying Kinetic chemistry (and most of the Physical chemistry topics), we often find definitions based upon the mathematical formalism. For example, Order of reaction is often defined as the sum ...
0
votes
1answer
39 views
When reactants are in their transition state, can they go back into their reactants form instead of progressing to form the products? [closed]
When reactants are in their transition state, can they go back into their reactants form instead of progressing to form the products? I don't see any reason why the reaction has to keep progressing ...
1
vote
1answer
59 views
Chemical equilibrium ā why multiplication, rather than addition? [duplicate]
Why do we multiply (and not take the sum) the concentration of products and reactants when more than one entity is present in either side and rise the power to the coefficient term?
Suppose either
$$...
0
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1answer
40 views
How to properly model a mechanochemical reaction of barium titanate and copper(II) complexes?
I would like to understand, in terms of chemical kinetics, how I could equate the reaction rate between $\ce{BaTiO3}$ and copper(II) complexes under ultrasound effect.
Examples in literature would be ...
2
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1answer
47 views
Solution of a first- and second-order consecutive reaction scheme
I have a compartmental model system X, a simplified version of which, looks like this:
$$
\text{System }x: \enspace \text{STO} \xrightleftharpoons[k_2]{k_1} \text{blood} \xrightarrow[]{k_3} \text{...
2
votes
1answer
55 views
Effect of concentration on rate
How do I solve this question?
My thinking is this: since O2 is not a reactant in any step, and since the reaction rate depends only on the reactants, increasing the concentration of O2 does not ...
0
votes
1answer
36 views
Question on notation
Here, when they write $v/(\mathrm{mol\ s^{-1}\ (kg\ \text{protein})^{-1}})$ is $0.30$ for the first row first column, do they mean that the value is $0.30\ \mathrm{mol\ s^{-1}\ (kg\ \text{protein})^{-...
0
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0answers
38 views
Photoelectric effect question
My attempt:- 1)At 0.68e15 Hz frequency of light,Metal A gives 7.2eV Kinetic Energy(KE).
2)At 1e15 Hz frequency of light, Metal B, gives 6eV Kinetic Energy.
3) At 1.1e15 Hz frequency of light, Metal ...
1
vote
1answer
32 views
Electron transfer rates in Marcus Theory [closed]
Electron transfer rates (k) as derived from Marcus theory assumes i) thermal equilibrium and ii) neglects quantum nature of low-frequency phonon modes. Can anyone explain what is at the heart of these ...
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1answer
49 views
Is dimerization just a synonym for asscociation with n=2? [closed]
Association is a process of the form
$$\ce{nS<=>S_n}$$
Is dimerization refering to only the special case $n=2$ or is it synonymous for $n\in\mathbb{N}$?
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1answer
31 views
Is it necessary that hydrolysis of ester will only take place in excess of water?
I was given a question on chemical kinetics in which the statement was given-
"The Concentration of water in hydrolysis of ester does not change to much extent"
I marked the statement to be false ...
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votes
1answer
58 views
I need explanation for reaction rate [closed]
That's a sample reaction:
$$2N_2+3O_2->2N_2O_3\ \ \ r=k_1[N_2]^2[O_2]^3$$
Why can't I write this as
$$N_2+\frac{3}{2}O_2->N_2O_3\ \ \ r=k_2[N_2][O_2]^{\frac{3}{2}}$$
Don't bother the elements. ...
2
votes
2answers
45 views
Is equilibrium constant at a given temperature derived from Gibbs free energy of reaction valid for doing simple kinetic modelling?
I intend to do a kinetic study of simple alcohol catalytic dehydrogenation reactions in the gas phase. I want to start with simple power law kinetics using $K_\mathrm{eq}$ to account for the ...
0
votes
2answers
54 views
Can I determine the rate law order from stoichiometric coefficients?
I've read in two books, and seen in three separate videos courses, that you cannot determine the rate law order from stoichiometric coefficients.
Then, I have seen homework and "practice" problems ...
2
votes
1answer
89 views
How to set up an equation to solve a rate law computationally?
I am confused on how to set up my equations to use in the solver. I have an equation
$$\ce{A + 2B -> C}$$
As a given, it is first order in A and second order in B. What I need to do is to solve for ...
1
vote
0answers
34 views
What is the activation energy of a Daniell cell?
I'm having trouble finding a posted literature value for the activation energy for the Daniell cell redox reaction:
$$\ce{Cu^2+ + Zn -> Cu + Zn^2+}$$
Where might I be able to find this ...
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votes
1answer
39 views
What is the molecularity of a reaction if it has a fractional order as per rate equation? [closed]
The rate equation of any reaction is found by using its slowest step.
My book says that molecularity of the slowest step of a reaction is equal to the order of the same reaction.
However, there are ...
2
votes
1answer
52 views
Rate of reaction involving different stoichiometric coefficients
Suppose I have a reaction (Say it is the Haber process):
$$\ce{N2 + 3H2 <=> 2NH3}$$
If we have to calculate the average rate of reaction of the above we follow the reasoning the rate of ...
0
votes
1answer
40 views
Rate determining step for parallel reaction?
I have always read that the rate determining step is the slowest step in a reaction (source: Wikipedia).
In chemical kinetics, the overall rate of a reaction is often approximately determined by ...
2
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0answers
22 views
Order of Reaction differs in equation and linearisation
I have given the following equation: $A + 2B \rightarrow C$
$ v = āk\cdot [A]\cdot[B]^2$
gives me the orders 1 for A and 2 for B. That results in a total order of the reaction of 3.
So far so good. ...
2
votes
2answers
56 views
How does the rate constant change with the change of the temperature?
In class, we discussed the following multiple-choice question.
The rate expression for a reaction is:
$$rate = k[X][Y]$$
Which statement is correct?
A. As the temperature increases, the ...
1
vote
1answer
59 views
How to derive the steady-state solution for simple two-step reaction with differential equations? [closed]
Consider this simple two step reaction, a variant of a Michaelis-Menten type of problem, where $\ce{A}$ and $\ce{B}$ reversibly bind to make $\ce{AB}$, and $\ce{AB}$ and $\ce{C}$ reversibly bind to ...
4
votes
2answers
204 views
General justification for steady state approximation
I want to understand the assumptions that have to be fulfilled in order for the steady state approximation to work. I did some research myself and was able to deduce assumptions of the form $k_1\gg ...
