Questions tagged [kinetics]

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

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What happens when solution containing two or more cations are electrolysed at an excess potential?

$\pu{250 mL}$ of a waste solution obtained from the workshop of a goldsmith contains $\pu{0.1 M}$ $\ce{AgNO3}$ and $\pu{0.1 M}$ $\ce{AuCl}$. The solution was electrolyzed at $\pu{2 V}$ by passing a ...
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Steady State: Exclusion of Term

Synopsis We are given a proposed mechanism for the condensation of $\ce{(CH_3)_2CO}$ as follows First Step: $$\ce{(CH_3)_2CO + OH^- <=> CH_3C(O)CH_2^- + H_2O}$$ Second Step: $$\ce{CH_3C(O)CH_2^- ...
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How to learn the concept behind Thermodynamics, Equilibrium, Electrochemistry, Chemical Kinetics [closed]

I am currently reading Thermodynamics, Chemical Equilibrium, Ionic Equilibrium, Electrochemistry, Chemical Kinetics for JEE Advanced exam in India. Now when I am solving problems I can not inter ...
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Activity of Polonium in half-time in Becquerels

I got an exercise but I don't know the exact answer. In the catalog note of the reference source of Polonium-210 radiation with a half-life of 138 days, it was stated that one day the activity was $\...
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Temperature change vs time in first order reaction [closed]

Please tell me how to write a formula for the variation of the temperature (T) as a function of time (t) and E. for a first-order reaction by linking it with Arrhenius equation and Eyring Equation as ...
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Why a catalyst is not consumed in a reaction when all steps are reversible?

It is said that a catalyst speeds up the rate of a reaction but is not consumed (assuming no side reactions take place). Suppose we have the following reaction: $$\ce{A + B <=> C} $$ catalysed ...
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Relation between Temperature from the Arrhenius equation of the first order reaction and the time taken by the reaction [closed]

Consider the chemical transformation of a gas A to a gas B: 𝐴→𝐡 π»π‘’π‘Žπ‘‘ π‘œπ‘“ π‘Ÿπ‘’π‘Žπ‘π‘‘π‘–π‘œπ‘›; Ξ”π»π‘œ=βˆ’1000π½π‘šπ‘œπ‘™, Ξ”π‘†π‘œ=100π½π‘šπ‘œπ‘™πΎ. The enthalpy and entropy of the reaction are temperature ...
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Equilibrium constant of a reaction whose order of forward and reverse reaction is not same

Suppose, a reaction is like, $$\ce{aA + bB <=> cC + dD}$$ and that A, B, C, D all are gas. Now it is known that: $$K_c = \dfrac{[A]^a[B]^b}{[C]^c[D]^d}$$ Now if the forward reaction is second ...
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Is standard change in activation Gibbs free energy indepedent of pressure?

For a chemical reaction the activation volume is defined as: $$Ξ”^{\ddagger}V={V^\ddagger}-V$$ where both $V^\ddagger$ and $V$ refer to standard states (I have omitted the symbol for simplicity). One ...
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kinetic description of an autocatalytic system

I have previously asked this question at physics SE here and it was suggested to post it here. I am looking at the system: $2X + Y \Leftrightarrow 3X $ $A \rightarrow Y$ $X \rightarrow B$ The ...
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adiabatic reversible process problem

A compressor recieved air at To= 300 K and at pressure Po= 1 atm. At the exit, P1 = 2 atm. The process inside the compressor is (A) adiabatic and reversible (B) gas is an ideal gas (3) gamma = Cp/Cv = ...
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Why are the “extents of reaction” the same for all reactants and products?

Consider the follwoing reaction: $$\ce{a A + b B -> c C + d D}\tag{1}$$ where $\ce A$ and $\ce B$ are the reactants, $\ce C$ and $\ce D$ are the products, and $a (<0)$, $b(<0)$, $c(>0)$, ...
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New relationship between exponential factors and entropy of a reaction?

Consider the reaction $\ce{A <=> B}$. Let $k_f$, $E_A$, and $A$ denote the forwards rate constant, activation energy, and pre exponential factor, respectively. Let $k_r$, $E_A'$, and $A'$ denote ...
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Reversible equation in Chemical Kinetics β€” Should I use definite integral when solving the differential equation?

I found this problem: We have the following reversible reaction: $A \ce{<=>[\ce{k_1}][\ce{k_2}]} B $, described by the kinetics equation: $$\frac{d[X]}{dt} = k_1([A]_0-[X])-k_2([B]_0+[X])$$ ...
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Getting close to zero percent of particles with energy greater than an activation energy of 101kJ/mol using the Maxwell-Boltzmann energy distribution

I experimentally obtained the activation energy of a reaction to be approximately 101kJ/mol. I was then going to use the value for the activation energy to see how the number of particles with ...
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Receptor and Ligand Binding

Hope this is the right place to ask. I'm reading chp. 2 of 'Receptors, models for binding, trafficking, and signaling' by Lauffenburger. In it they describe a situation where there are ligands that ...
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Determine the rate law for the given reaction

I was studying for a PhD entrance exam and this question made me wonder about some topics in kinetics: Consider the multi-step reaction below: $\ce{A_2 β†’ 2 A}$ $\ce{2A + X β†’ Y + B}$ $\ce{B β†’ A2 + Z}$ ...
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Relationship between molecularity and the reaction order

Should the molecularity be equal or less than the reaction order? Consider the reaction: $$\ce{H2(g) + I2(g) β†’ 2 HI(g)}$$ If we consider the mechanism of this multi-step reaction, the molecularity is ...
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Frequency Factor of the Arrhenius Equation

The question came to my mind as to whether the effect of a catalyst on a reaction included the modification of the frequency factor (or pre-exponential factor) of a reaction, shown in Arrhenius' ...
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Concentration and rate constant

E.g. for a first-order reaction, rate of reaction = k[A], I can see that a higher concentration of A leads to a higher rate due to an increased chance of effective collision. According to this, ...
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Activation energy and degrees of freedom

According to the Arrhenius equation the rate of a reaction increases as at higher temperature a greater percentage of molecules have translational kinetic energy greater than or equal to activation ...
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Rate of change and kinetics order of reaction question

The rate of reaction is given by the following equation, where [Ker-S-S-Ker] is just the molecule being broken down and [RSH] is an abbreviation for thioglycolic acid The thioglycolate is in large ...
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Concentration of sulfur in turbid solution

I recently participated in an experiment where I need to calculated the reaction orders and the reaction constant of the reaction: $$\ce{8 Na2S2O3(aq) + 16 HCl(aq) -> S8(s) + 8 SO2(g) + 16 NaCl(aq) ...
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when is a system of mass-action reactions guaranteed to satisfy detailed balance?

when does a system of mass-action reactions satisfy detailed balance for any non-zero choice of the rate constants? consider a trivial example: $X + Y \ce{<-->[k1][k2]} XY$ satisfies detailed ...
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Why are we finding the integrated rate law by starting with r=k[A]?

When deriving the integrated rate equations, we start off with r =k[A] for example, and then we do the whole integration thing to find an equation of [A] in terms of time. But why are we ingnoring any ...
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Role of catalyst in elementary reactions towards rate law

We do know that the concentration of a catalyst might affect the rate of reaction. But what if the catalyst is included in the rate law? For example, $$\ce{O3 + M <=>[$k_1$][$k_{-1}$] O2 + O + M}...
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Confusion over the rate law

I am really confused about the rate law. From my understanding, the rate law gives an equation that tells us the rate of the disappearance of the reactants. So, for example, the rate law of the ...
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Determine the order of reaction [duplicate]

Is there any formula that can help determine the order of the reaction? Cause my teacher told me to plot line chart. So, I am curious about another method that doesn't use line chart (like formula ...
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Can rate constant depend upon the concentration of reactants (or other species involved in the reaction)?

Transition state theory tells us that the rate constant of an elementary step is $$\ce{k_r=\frac{\kappa k_BT}{h}e^\frac{- \Delta G^\ddagger}{RT}}$$ where $\ce{\Delta G^\ddagger}$ is the activation ...
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Why is a third body needed in the recombination of two hydrogen atoms?

In the article Discuss. Faraday Soc. 1962, 33, 205, the authors say that in order to form molecular hydrogen from collision to atom we need a third body to remove the excess energy. That is we have ...
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Rate expression with water as one of the reactants

When finding an equation for d[A]/dt from reaction mechanisms and $\ce{H2O}$ is a product/reactant, does $\ce{H2O}$ have to be included or left out like for equilibrium constant expressions? For ...
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Is order defined for a reaction which does not follow power law dependence?

As per my knowledge , order of a reaction is the sum of exponents of all the terms in rate law of the reaction But reaction which do not follow power law dependence , for example , formation of HBr , ...
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Parallel reactions for one product

For me it is clear how I could solved the kinetic of a parallel reaction like this But, how can I solve if this would be the case: Thanks in advance!
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Organic-catalysis microwaves [closed]

When we perform a organic reaction without any addtional catalyst except that the reaction is carried out under microwave condition we can accelerate this reaction in comparison with one under heating ...
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Rate law for A + B β†’ C β†’ P

I need some clarification for the following assignment: Derive the rate law for $$\ce{A + B -> C -> P}$$ when $\ce{A + B -> C}$ is the slowest step and very slow. My understanding is $\ce{A ...
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How does it affect the equilibrium expression if the concentration of any component remains the same?

I am a high school student and I am very confused in Equilibrium expression, My confusion is that "Why we don't write concentration of solids and pure liquids in equilibrium expression?" ...
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Is this statement valid for reactions of all orders? [duplicate]

My textbook (not an international standard) states that for the first order reactions only The quantity of reactant remaining after $n$ half lives is $$A_n = \frac{A_0}{2^n},$$ where $A_0$ is the ...
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Is it easier to mix a solution that is in the liquid or in the vapor phase?

In the article on dilution, Wikipedia has the following statement: The same direct relationship applies to gases and vapors diluted in air for example. Although, thorough mixing of gases and vapors ...
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How do I compute the mean dissociation time from the dissociation constant, assuming instantaneous binding reaction rate?

There is a solution with two chemical species, A and B. Given the equilibrium dissociation constant $ K_D=\frac{[A][B]}{[AB]} $ how do I relate the mean dissociation time $t_{off}$ to $K_D$, and ...
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Can reversible reactions proceed by different mechanisms in the forward and reverse directions? [closed]

It seems odd to me that this would be the case, but it also seems odd that it wouldn't. Imagine a mechanism for a (forward) reaction that includes a slow reversible step and a fast irreversible step: ...
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Brownian motion modeling of surface reaction

I am interested in simulating a reaction-diffusion system, where particles subjected to Brownian motion can react when they reach a specific surface. The reaction is simple: A $\rightleftharpoons$ B ...
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how to derive equilibrium concentrations from initial conditions for mass action reactions?

I am reading a tutorial on biochemical reactions and mass action kinetics (https://www.math.utah.edu/~keener/books/control.pdf, pp. 1-2) and would like to derive an analytic solution to confirm ...
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Wiki’s explanation of the rate of chemical reaction [closed]

Could you please help me understand the Wiki’s explanation of the rate of chemical reaction? It says: the rate of the chemical reaction is directly proportional to the product of the activities or ...
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Does it make sense to differentiate the Arrhenius equation with respect to temperature?

I am trying to answer the question: "between concentration and temperature, which has a greater significance on the rate of reaction" Hence, I'm trying to find a method to systematically ...
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Understanding transition state theory

Let's say we have standard chemical reaction given by $$A-B + C \leftrightharpoons [A\cdot\cdot B\cdot\cdot C]^{\dagger} \rightarrow A +B-C$$ I want to estimate the pre-exponential factor of this ...
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Why does activation energy depend on temperature? [duplicate]

To me it makes sense that the activation energy $E_\mathrm a$, as given by the Arrhenius equation, doesn't depend on the temperature as the needed energy (potential energy) to start a reaction has ...
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Kinetics question regarding Rate Law

The acid catalysed hydrolysis of an compound $\ce{A}$ at $\pu{303K}$: $$\ce {A ->[$k$] B}$$ has a half-life of $\pu{100 min}$ when carried out in a buffer solution of $\mathrm{pH=5}$ and $\pu{10 ...
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Deriving an expression for reaction time in terms of the total concentration

Consider the dimerization of protein $\ce{A}:$ $$\ce{2A <=> A2}$$ with forward rate constant $k_1$ and backwards rate constant $k_{-1}.$ Derive the following expression for the reaction time in ...
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Kinetics of Decomposition of Hydrogen Peroxide [duplicate]

Consider the decomposition of Hydrogen Peroxide: $$\ce{H2O2 -> H2O + 1/2O2}$$ The rate law for this reaction is : $$\text{Rate} = k[\ce{H2O2}]$$ Further $$\text{Rate} = -\frac{\mathrm d[\ce{H2O2}]}...
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Solving for Concentration Using pseudo-First Order Kinetics

The following graphs represent a pseudo-first order bi-molecular reversible reaction with the formula $\ce{A + B <=> C}$: The reaction product has an extinction coefficient of $\pu{50000 M-1 cm-...

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