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Questions tagged [kinetics]

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

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Linear Equation for an Overall Third-Order Reversible Reaction

For the reaction: aA <--> bB With reaction order (m) with respect to substance A; m = 2 (forward reaction) and reaction order (n) with respect to substance B; n = 1 (backwards ...
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what the solution of this problem, negative absorbance values in UV-vis spectrum

In my project, I take the UV-visible spectrum of reaction between pyridinium chlorochromate and N-acetylcysteine. In some wavelengths, the absorbance value is negative for example it is (-0.006, -0....
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Using Maxwell–Boltzmann distribution in reacting systems

In the book Physical Chemistry, a Molecular Approach by Simon and McQuarrie, the have used the Maxwell–Boltzmann distribution for velocity of molecules to estimate the the rate constant of a reaction. ...
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1answer
33 views

Inactivation of enzyme: Why inactivation constants do not follow the Arrhenius equation? [closed]

The Arrhenius equation may not account for the temperature effect on thermal inactivation rate constants. Why can the thermal inactivation kinetics not be expected to follow Arrhenius? The reason that ...
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Rate law equation - orders?

Consider the following reaction: $$\ce{2 H2 (g) + 2 NO (g) -> N2 (g) + 2 H2O (g)}$$ The elementary steps of this reaction are: $$ \begin{align} &1^\text{st}~\text{step:} &\ce{...
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Boltzmann factor vs. graph of Maxwell–Boltzmann distribution

In discussions of the Arrhenius equation describing how rates change with temperature, there is often a reference to collision theory. In the Arrhenius equation, $$ k = A e^{-\frac{E_\mathrm{A}}{R T}...
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51 views

Which rate, the forward or reverse rate of acid dissociation, is more strongly affected when diluting acetic acid in aqueous solution?

Acetic acid is a weak acid. It is in equilibrium with acetate and hydronium ions in aqueous solution: $$\ce{CH3COOH(aq) + H2O(l) <=> CH3COO-(aq) + H3O+(aq)}$$ Ostwald's law states that the ...
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Does the starting concentration in a isochoric container depend on the pressure?

Given is the following reaction of carbonic acid and carbon dioxide: $$\ce{RCOOH (g) → RH (g) + CO2 (g)}$$ The reaction rate of this decarboxylation was measured in a container with constant volume ...
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1answer
20 views

Determining the concentration after half-life period

I was given the reaction In diluted solution and with neutral pH, the reaction reacts according to a reaction velocity law of pseudo-1. order: $$-\frac{dc_{DNPA}}{dt}=k_{obs},\quad k_{obs}=k\cdot c_{...
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1answer
67 views

Probability of the single molecule reaction to happen

I am trying to simulate the single particle second order reactions with known rate constants $k_1$ and $k_{-1}$ in Python. The point of this simulation is to fit the real experimental data to the ...
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1answer
62 views

High concentration of ferric ion catalyst decreases rate of decomposition of hydrogen peroxide in the Fenton reaction

I did a project on the Fenton reaction and rate of decomposition of $\ce{H2O2}$. I used colorimetry to measure the rate of decolourisation of methylene blue when I mixed $\pu{5e-6 mol}$ $\ce{FeCl3}$ ...
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59 views

Flow rate of the fuel consisting of ethanol and water burning in air of a given flow rate

I hope that someone could give me some hints or tips on how to approach this question, even though these types of questions are usually closed off as homework. A burner is run by a fuel mixture of $...
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Must a sample of a deuterated compound be isotopically pure for kinetic isotope experiments?

I'm trying to do a project on the primary kinetic isotope effect on the dehydroxylation of $\alpha-FeOOH$, goethite. The goethite consists of edge-sharing double octahedra of 3 oxyanions and 3 ...
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44 views

First Order Chemical Kinetics

I have the following system of reactions: \begin{align} M & \xrightarrow{\lambda(M,W)}M+M \\ W & \xrightarrow{\lambda(M,W)}W+W \\ M & \xrightarrow{\mu} \emptyset \\ W & \xrightarrow{\...
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1answer
42 views

How to calculate the kinetic order of an enzymatic reaction?

This question is concerning the metabolism of ethanol by an alcohol dehydrogenase enzyme. Usually people metabolize alcohol equivalent to "one beer per hour". One beer is said to contain 33cL. The ...
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Calculation of rate constant for bimolecular reaction from Gaussian DFT calculations

I am working with a bimolecular reaction for which I have computed the energy profile. I have output files for TS and reactants which I intend to use for rate constant calculations. From TST we have: ...
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1answer
51 views

Dependence of rates of neighbouring group participation on length of alkyl chain

On the topic on neigbouring group participation, it is mentioned in Carey & Sundberg (2007)[1] that the effectiveness of the participation is dependent on on the ease with which the molecular ...
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Why is sublimation considered a zero-order process?

In my Chemistry book, it states that sublimation is normally a zero-order reaction or process, as the concentration of molecules that have sufficient energy to sublime is limited by the solid's ...
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In zero order why we don't need the coefficient of reactant in integration of rate law?

For a reaction: $\ce{aA->product}$ The rate law is $\text{Rate}=-\dfrac{\mathrm d[A]}{a\,\mathrm dt} = k$ Where: $k$ is the rate constant $[\ce{A}]$ is the concentration of the reactant $\ce{A}$...
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1answer
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Is it possible to turn food into fuel for a combustion engine? [closed]

According to McDonald's Nutrition Calculator page, the following order would contain 2480 kilocalories (or 10376 kilojoules): 1 x Double Bacon Smokehouse Burger 1 x Large Chocolate Shake 1 x Large ...
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1answer
39 views

Neuter Reactants: What do they do?

So imagine a hypothetical chemical equation $$ A + B \rightarrow C + B $$ It is obvious from the equation that $B$ is not consumed during the reaction. If $B$ actively take part in the reaction, if ...
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1answer
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Why do bubbles form on the side of a plastic bottle?

I have a plastic bottle filled with drinking water where only one side of the bottle has air bubbles. I know that water is not pure and there are dissolved gases, and my theory is that there are small ...
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Electrophillic Iodination

I read that the Iodination of C6H6 (in presence of FeCl3) has a higher rate constant than C6D6 (in presence of FeCl3) in a book. It has mentioned without much explanation by simply stating that its ...
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62 views

How to derive rate law expression for inversion of sucrose with changing pH?

I came across a question worded as follows- "The inversion of cane sugar proceeds with half life of 50 minutes at pH=5 at any concentration of sugar. However, if the pH=6, the half life changes to 500 ...
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39 views

The mechanism of the reaction between 2-chloroethanol and hydroxyl ions in aqueous solution

The mechanism of the reaction between 2-chloroethanol ($\ce{CH2ClCH2OH}$) and hydroxyl ions in aqueous solution forming ethylene oxide ($\ce{CH2CH2)O}$ probably contemplates two steps: $\ce{...
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2answers
61 views

Order Of Reaction [closed]

A+B ———> C+D If A and B are taken in excess then what will be the order of reaction? I thought since it is taken in excess, their change wont really be significant and so answer would be 0.
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1answer
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Rate constant converion [closed]

I need to calculate the half life for a first order reaction for which I need the rate constant $k$. From literature I observed that for a very closely simulated experiment I obtained the numerical ...
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1answer
173 views

Can Le Chatelier's principle be derived?

Le Chatelier's principle says : If a constraint (such as a change in pressure, temperature, or concentration of a reactant) is applied to a system in equilibrium, the equilibrium will shift so as ...
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1answer
40 views

Why is the equilibrium constant being calculated differently here?

In my NMR textbook, it says the equilibrium constant for a dynamic process (e.g., A in equilibrium with B) is calculated by the concentration of A divided by the concentration of B. Is this a typo? ...
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2answers
82 views

How would you determine the RDS from the rate and order of a reaction [closed]

I know what a rate determining step is, and also have knowledge about zero order and first order reactions. But, in one of my tests, I was unable to solve the following question: A hypothetical ...
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1answer
67 views

How is the reaction rate constant affected by concentration?

Consider the concentration-time dependence graph for two first-order reactions. Which reaction has a larger rate constant? Unable to determine The reaction represented by the ...
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Which is more soluble in water ammonia or Sodium dodecyl sulfate

I've tried looking this up and can't seem to find the solubility of SDS if any one knows the answer I would really appreciate it. Which is more soluble in water ammonia or Sodium dodecyl sulfate. ...
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1answer
31 views

Reaction rate coefficient constant multiplier for equation with multiple atoms consumed?

For the elementary reaction $\ce{2O -> O2}$, when calculating the rate of concentration change of atomic oxygen as $\frac{d[O]}{dt}$, would I use the standard rate coefficient $k_f$ or would I have ...
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2answers
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Explanation for the derivative of kinetics equation

I'm working with a first rate law expression. A + B -> C Given: $k_1[A][B]=k_{-1}[C]$ which means $[C]=\frac{k_1[A][B]}{k_-1}$. The book says $\frac{d[C]}{dt}=k_1[A][B]-k_{-1}[C]$ which is where ...
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How to derive Arrhenius equation from hard-sphere collision theory

Reading the description of the Arrhenius equation from Wikipedia: ...One example comes from the collision theory of chemical reactions, developed by Max Trautz and William Lewis in the years 1916-...
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1answer
54 views

Can we interpret the “extent of reaction” as the number of reactions that happened?

Consider this reaction: $$\ce{\alpha\ A + \beta\ B -> \omega\ C + \delta\ D}$$ Where $\ce A$ and $\ce B$ are the reactants, $\ce C$ and $\ce D$ are the products, and $ \alpha, \beta, \omega, \...
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1answer
542 views

What is the rate-determining step in free radical halogenation?

Recently, we were learning about free radical halogenation in school. A set of notes given to us wrote that the rate-determining step is the propagation step. This seems to go against my understanding ...
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Show that this mechanism is consistent with the rate law - how to?

The problem is from Principles of general chemistry, 2nd edition by Silverberg, chapter 16 problem no.81: "Even when a mechanism is consistent with the rate law, later work may show it to be ...
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112 views

Calculate Rate constant, k, for a consecutive reaction where k1<<k2

I have a consecutive reaction where the first step is the rate determining step so $k_1<<k_2$: $$\ce{A ->[$k_1$] B ->[$k_2$] C}$$ The rate law can be shown to be: $$[\ce{C}] = {1 - \exp(...
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A doubt regarding coefficients in rate law expression

For example, for the reaction $\ce{A + 2B -> C}$, we have $$\text{rate} = -\frac{1}{2}\frac{\mathrm d[\ce{B}]}{\mathrm dt} \quad \text{and} \quad \text{rate} = k[\ce{A}]^x[\ce{B}]^y.$$ Together, ...
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1answer
44 views

Current in a Lithium Ion Battery

I am trying to find the current transferred to the anode and cathode of a Lithium Ion Battery at different voltages. I know the temperature (approximately) of the battery, the battery's starting ...
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1answer
43 views

Rate of a reaction [duplicate]

We know that the rate of a reaction $\ce{aA + bB -> cC + dD}$, the rate of the forward reaction is given by $r_\mathrm f = k_\mathrm f[\ce A]^p[\ce B]^q$ where $ a\neq p$ and $ b\neq q$ according ...
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1answer
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Is it possible to apply reaction progress kinetic analysis on non catalytic reactions?

I was wondering if anyone familiar with reaction progress kinetic analysis knows if it is possible to apply the method on non catalytic reactions, and if so provide a few references with relevant ...
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1answer
158 views

What is 'power law' kinetics?

I've come across a lot of instances where 'power law' description of the kinetics was mentioned, but I cannot think of any integrated rate law that follows something like: $$A(t)=bt^n+c$$ I'm pretty ...
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When are transition state's energy barrier “reasonable” at a certain temperature?

Every computational chemist who does a little bit of mechanistic studies has asked himself this question. When you obtain your first transition state and look at the activation barrier needed to ...
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2answers
428 views

Does the rate constant depend on pressure?

I have read in some books that when pressure increases, the number of effective collisions increases. Hence, $k$ depends on pressure. Is it true? If so, then why doesn't $k$ depends on concentration? ...
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Order of a complex reaction [duplicate]

Is the order of a complex reaction determined by the slowest step always? Is it so that order of a reaction is determined by rate determining step and since in a complex mechanism, we write elementary ...
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3answers
132 views

In regard to collision theory, why do molecules have to have the correct orientation in order to react?

Hypothetically speaking, if a reagent in a bimolecular reaction has enough energy to break the bond of the other reagent but is orientated in the wrong direction, why does the bond not break? Does the ...
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36 views

Does the ignition temperature of a substance decrease with the concentration of oxygen?

Is it possible for a substance to undergo combustion at a temperature lower than its ignition point if the concentration of oxygen increases?