Questions tagged [kinetics]

The study of rates and steps in mechanisms of chemical processes.

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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.
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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 ...
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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?
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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} +...
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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 ...
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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 ...
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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 ...
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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-...
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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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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 ...
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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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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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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 ...
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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 ...
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Production rate of parallel reactions

The degradation of hydrogen peroxide in water $\ce{(2 H2O2 (aq) → 2 H2O +O2 (g))}$ can be catalyzed by $\ce{Br-}$ and $\ce{H3O+}$. Derive an expression for the production rate for the following ...
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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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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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Find order of reaction 2A → 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 ...
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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 ...
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1answer
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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 ...
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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 ...
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3answers
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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 ...
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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. I’d have thought that evolution would have selected for a “simpler” pathway with ...
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1answer
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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 ...
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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 ...
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1answer
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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 ...
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1answer
46 views

what is the physical significance of ∆H=∆U 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 ...
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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 ...
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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 ...
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1answer
59 views

Chemical equilibrium — 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 $$...
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1answer
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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 ...
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1answer
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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{...
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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 ...
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1answer
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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})^{-...
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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 ...
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1answer
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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
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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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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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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. ...
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2answers
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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 ...
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2answers
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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 ...
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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 ...
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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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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 ...
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1answer
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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 ...
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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 ...
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Order of Reaction differs in equation and linearisation

I have given the following equation: $A + 2B \rightarrow C$ $ v = –k\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. ...
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2answers
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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 ...
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1answer
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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 ...
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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 ...

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