Questions tagged [kinetics]

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

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Approximating entropy change in a reaction using Arrhenius equation

I am a high school student.Recently my teacher finished teaching the chapter Chemical kinetics in which I have gone through Arrhenius equation.Can we estimate the change in entropy using it? I have ...
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Kinetics of inversion of cane sugar

Question 1 The formula for concentration of cane sugar as a function of time is given by $$k = \left(\frac{2.303}{t}\right) \log\left[\frac{\alpha(0) - \alpha(\infty)}{\alpha(t) - \alpha(\infty)}\...
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rate of reaction and RDS

An article on Khan-Academy, states the following: The overall reaction rate is determined by the rates of the steps up to (and including) the rate-determining step Here, it says that rate is ...
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Factors affecting rate of β-elimination reaction with alcoholic KOH

The question asks for the rate of reaction in $\beta$-elimination using alcoholic $\ce{KOH}$. Arrange the following alkyl halides in decreasing order of rate of $\beta$-elimination reaction with ...
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What is the physical explanation driving current flow in a concentration cell?

In a galvanic cell, current is driven because the species at the cathode is reduced by grabbing some electrons from the cathode. The cathode now lacks electrons so it pulls them from the anode. Now ...
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Dependance of stability for reaction rate

In our book, it is given: Organic compounds are generally less stable than inorganic compounds. Due to covalent bonding in them, their reaction rates are often slow. First, it is said that they are ...
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64 views

Does rate of auto-ionization of water change after adding a strong acid?

We know that a reaction could have different rates at equilibrium. For example, lets take the reaction: $$\ce{A + B -> C }$$ At equilibrium, the rates of formation and dissociation will be equal: $$...
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Catalysts and activation energy

Do catalysts increase rate of reaction only by decreasing activation energy? Or can they affect the Arrhenius factor or reaction orders? Like if one catalyst is more effective at increasing rate of ...
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Equilibrium constant for heterogeneous equilibria having aqueous as well as gaseous reactants

Suppose we have a heterogenous equilibrium : $$\ce{A(aq) +B(aq) <=> C(g) +D(aq)}$$ Which equilibrium constant is used here? Both pressure and concentration terms are there. So, according to me, ...
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Finding the ratio of rate constants [closed]

A group of mountain climbers set up a camp at a $\pu{3 km}$ altitude and experience a barometric pressure of $\pu{0.69 atm}$. They discover that pure water boils at $\pu{90 ^\circ C}$ and that it ...
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Finding time t in a first order reaction (JEE Adv 2019) [closed]

The decomposition reaction $\ce{2N2O5(g) ->[\Delta] 2N2O4(g) + O2(g)}$ is started in a closed cylinder under isothermal conditions at an initial pressure of $\pu{1 atm}$. After $\pu{Y \times 10^{3} ...
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Electrolysis of aqueous solutions

Water competes with any ions in solution for both oxidation and reduction. There are $1000\ \mathrm{g\ l^{-1}}/18\ \mathrm{g\ mol^{-1}}\approx55.56\ \mathrm{mol\ l^{-1}}$. That is truly huge in ...
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Half life of first order reaction in case of variable volume [closed]

I have a doubt about the meaning of half-life of a first-order reaction. Earlier I used to think that it is the time in which concentration of reactant reduces to half of its initial but recently I ...
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How can I analytically calculate the rate of thermal decomposition of calcium carbonate?

I am a first-time poster on Chemistry StackExchange, and not much of a chemist. I'm trying to determine the rate of thermal decomposition (in mol/s) of calcium carbonate ($\ce{CaCO3}$) at various ...
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Kinetics of Sabatier reaction

I am modelling a methanation process in MATLAB, where I have a rate equation for methanation $$\ce{CO2 + 4 H2 → CH4 + 2 H2O}$$ in which I need partial pressure of $\ce{CO2},$ $\ce{H2},$ $\ce{CH4},$ $\...
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How are half lifes calculated for radioactive substances that decay over many years [duplicate]

How are the half lives (or whole lives) calculated for slowly decaying radioactive substances such as tellurium? I must be having a fundamental misunderstanding of how we are able to predict the ...
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56 views

Finding the sensitivity of zero-order ultra sensitivity and its parameter dependence

I am provided a one-dimensional reaction system showing zero-order ultra sensitivity. $$\ce{X_1 ->[f_1] X_2}, \quad \quad \quad \ce{X_2 ->[f_2] X_1}$$ The reaction rate function is the reduced ...
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The interactions of the high energy gas particles

When we are talking about the idealization of the gas, why for high temperatures its particles interact less? I would say you have a bigger probability of the collisions among particles. Quantum ...
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1answer
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Why do isotopes have different chemical reaction rates? [duplicate]

Isotopes of a given element differ in the rates at which they undergo chemical reaction. Why is this so? The only explanation I could think of is that the gravitational force on the electrons ...
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Do tert-butylcyclohexanes with a leaving group locked in the equatorial position undergo E1?

Background Elimination of 1-bromo-tert-butylcyclohexane is a prototypical example of how important the anti periplanar relationship is for E2. From Organic Chemistry: Structure, Mechanism, Synthesis ...
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66 views

Chain transfer agents and rate of free radical polymerization

In free radical addition polymerizations sometimes chain transfer agents are added. From what I understand chain transfer agents (e.g. XR' below) reduce the average molecular weight by transferring ...
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Half-life and shelf-life of second-order reaction

For integrated rate laws, I have attempted to find the shelf-life and half-life of second-order reaction: However, the answers I have obtained (which are labelled with a red cross) are very different ...
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146 views

Why does a first order reaction only depend on the concentration of a single reactant?

I am new to kinetics so please explain it from basic, If there is a reaction - $$\ce{A + B + C -> D}$$ In first order reaction rate is given by- $\mathrm R = k[\mathrm A]$ or $\mathrm R = k[\...
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Can the Belousov-Zhabotinsky reaction be simulated with the Brusselator?

I'm trying to simulate the Belousov-Zhabotinsky reaction mathematically, with a system of ODEs. I know how to do this with the Oregonator and now I'm looking for another model to simulate the BZ-...
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Example of chemical reaction with a given form for the kinetic equations

I’m an applied mathematician looking for examples from various applications fields (right now, chemistry, obviously) to illustrate the following reaction-diffusion system $$ \begin{cases} \frac{\...
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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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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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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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Determining Half-lifes from a graph

So I was studying for an exam I have thursday when I came across a question regarding half-life. I had previously thought that the definition of a half-life is the time it takes for the amount of ...
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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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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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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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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 order....
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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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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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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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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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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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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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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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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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