Questions tagged [kinetics]
The study of rates and steps in mechanisms of chemical processes.
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Mass action law and conservation of mass
I am starting to learn about the use of mass action law in chemistry. I am doing some exercises to practice. In particular, I am considering the reaction
$$2 X \underset{3}{\stackrel{4}{\...
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What are the differences between the different Rate Equations?
I currently am about to finish general chem 2 so my knowledge is still basic.
There are different kinetics and rate equations and im not quite sure I know the differences.
Breaking rate of a reactant:...
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Enamine formation mechanism. Can't there be alternatives?
I'm studying organic chemistry, more specifically the imines and enamines. I've read about the mechanism of formation of enamine from a generic ketone and a question popped up in my mind. The ...
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How do metal hydrides behave in a non-hydrogen closed system?
I am curious about the fundamentals of metal hydrides and how adsorption/desorption works in non-hydrogen systems. My understanding is that the atom ratio M/Hx of the metal hydride is a function of ...
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Formation of hydrogen bromide: Does the concept of "order" apply to this reaction?
Started reading Levine's Physical Chemistry [1] yesterday, and I hit upon (another) wall.
On page 517, Chapter 15, she includes a reaction resulting in the formation of $\ce{HBr}$ from $\ce{H2}$ and $\...
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Are there exceptions to the rate law for elementary reactions?
According to several authentic sources (for example, ChemLibreTexts), for elementary reactions, the order is equal to molecularity according to the rate law.
Example: For an elementary reaction $$\ce{...
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How to model carbon sorption processes?
I am looking for a tool to simulate adsorption and desorption processes. Both chemical kinetics and the thermodynamics part are equally important. Is Cantera good for this? Can it model heat transfer ...
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How can the reaction heat be ignored in an energy balance?
I have received from my professor the following (summarized) problem:
A first-order exothermic reaction $\ce{A->B}$ took place in a typical tubular plug flow reactor (PFR). The tube was cooled to a ...
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How to write the balanced chemical equation for the system in a rate plot?
I have the rate plot below:
I know that $\ce{A}$ and $\ce{B}$ are the reactants, and $\ce{C}$ is the product. The textbook says that the balanced equation is $$\ce{3A + B -> 2C}\\[1em]$$ However, ...
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Which Gibbs' free energy is an activation energy diagram referring to?
In the case of activation energy diagrams in terms of potential energy, I understand that when we're talking about two individual molecules, the potential energy is highest in the transition state ...
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How to find the initial rate of a rate plot? [closed]
In the graph above, how do I find the initial rate of $$\frac{d[A]}{dt}$$
My balanced chemical equation is $$\ce{3A + B -> 2C}\\[1em]$$
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Chemical species equations in a kinetic mechanism of combustion
In combustion, for a kinetic mechanism involving $m$ reactions and $n$ chemical species, of the form
\begin{align}
\begin{cases}
\nu_{11}' \mathcal{S}_1 + \nu_{12}' \mathcal{S}_2 + \dots + ...
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How does stirring demonstrate a diffusion-controlled reaction?
I was reading about diffusion-controlled reactions, and on the Wikipedia page (Diffusion-controlled_reaction) it says the following:
"One classical test for diffusion control is to observe ...
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Effect of changing of the concentration of reactants when concentration of the initiator and the concentration of the initial reactant are very small
A + I---> p
What happens to the rate of the reaction when the concentration of the reactant is changed in a system that its concentration of its initiator and the concentration of the initial ...
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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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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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Effect of inert gas on the rate of reaction
Is there a general effect on the rate of reaction of a dynamic equilibrium when an inert gas is introduced at a constant volume? I know that the position of equilibrium won't change, but much like a ...
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Effectivness factor for a cylinder
I would like to demonstrate the effectiveness factor of a porous cylinder, for diffusion-reaction (only radial diffusion, 1st order reaction, isothermal, diffusion coeff. is constant, steady-state), ...
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Replacement for Centrifuge in Calcium Content Determination
Basically, I'm performing a lab investigation to determine calcium content in different milk sorts. Since my school didn't have any EDTA, I'm using Sodium Oxalate to form a precipitate with Calcium ...
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Finding the reaction order from a given plot of chemical kinetics
What will be the order of the reaction for a chemical change having $\log t_{1/2}$ VS $\log a$ Where $a=$ Initial concentration of reactant and $t_{1/2} =$ Half Life?
0 order
1st order
2nd order
None ...
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Rate law for A + B → C → 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 to find the current transferred to the anode and cathode of a lithium ion battery at different voltages?
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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Order of reaction with and without the presence of catalyst
When ethene reacts with hydrogen to give ethane in the presence of Ni, the order of the reaction is 2, if I am not wrong, please correct me if I am. But if we remove the catalyst, and simply allow ...
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Confused about underlying reasoning behind reaction quotient/equilibrium constant
I am a high school student taking AP Chemistry. In the unit on chemical equilibrium, there is much emphasis placed on calculating reaction quotients and equilibrium constants using this method: $$aA + ...
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Strange behavior of equilibrium constant when most of the components are solids / pure liquids
Consider the reaction $\alpha A(g) + \beta B(s) +\gamma C(s) +\cdots \rightleftharpoons \delta D(s)+\epsilon E(s)+\cdots $, so the chemical equilibrium constant should be $\dfrac{1}{[A]^\alpha}$, ...
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Concentration dependence of electron transfer
Regarding a single electron transfer:
$$O +e^- \rightarrow R$$
We find the current dependent on the overpotential as specified by the Butler Volmer equation:
$$i = i_0 (exp(\frac{\eta}{b})-exp(\frac{-\...
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Derivation of Flory's Model for Linear Condensation of Polymers
I'm having some trouble understanding a part of Flory's model for linear polycondensation reactions. In his 1936 paper, he derives an expression for the probability of the existence of a particular $x$...
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Solving for Partial Pressure given first-order decomposition
From my GenChem practice exam:
Consider the following reaction:
$\ce{C4H8 (g) → 2C2H4 (g)}$
The first-order decomposition of cyclobutane to two molecules of
ethene has a rate constant of $\ce{9.20\...
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How to use Graham's Law to solve for time
A question from one of my GenChem practice exams:
"A 3.0 L sample of helium gas was placed in a container filled with a porous membrane. Half of the helium gas effused through the membrane in ...
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Kinetic Isotopic Effect in EAS
It is observed that rate of reaction of two isotopologues of benzene, $\ce{C6D6}$ and $\ce{C6H6}$, is the same for electrophilic aromatic reactions, as the deprotonation is not the rate limiting step. ...
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When does Van't Hoff's reaction rate rule not work?
I have a problem answering a question in my lab report.
The question is about the empirical van't Hoff's rule - what does it say and what are its limitations?
I managed to find online that the ...
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Activation energy of the reaction between magnesium carbonate and hydrochloric acid
I've been working on a project that uses some abnormal methods to calculate the activation energy using only one trial of an exothermic reaction.
However now that I've completed the lab, I want to ...
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Does activation energy vary with temperature for the reaction between oxalic acid and potassium permanganate?
I've always been taught that activation energy doesn't vary with temperature for reactions, as $E_A$ represents some specific energy required by particles so that they can react. However, I recently ...
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On Le Chatelier's principle
According to my textbook,
Increasing the concentration of the reactants increases the rate of forward reaction only to reestablish equilibrium (Le Chatelier's principle)
But doesn't that also ...
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Calculating rate constant for reaction between potassium permanganate and oxalic acid
I'm writing a lab report investigating the effects of temperature on the rate constant in the reaction between potassium permanganate and oxalic acid. For my practical I've measured the time of colour ...
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Equilibrium concentrations of CO and Cl2 by dissociation of phosgene
I am working through a problem set from MIT's open courseware course Principles of Chemical Science.
The question is:
Phosgene $\ce{(COCl2)}$ is a chemical warfare agent that decomposes by the ...
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Does manganese reacts with water at "not" standard conditions?
In my answer, I stated that manganese is said to not react with water under normal conditions although some sources say it reacts with water to liberate hydrogen gas. Does it implies that it reacts ...
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How does red iron oxide (Fe2O3) increase the burn rate of sugar rocket fuel?
My question is similar to this one, however that question seems to ask about how it improves combustion in general, not specifically with respect to sugar rocket fuel.
The answer to this question ...
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Mechanism of decomposition of N2O5
In my book mechanism of decomposition of $\ce{N2O5}$ was given like
\begin{align}
\mathrm{Reaction:}\\
\\
\ce{2 N2O5 &-> 4 NO2 + O2}\\
\\
\mathrm{Mechanism:}\\
\\
\ce{N2O5 &<=>[k_1][...
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Reaction rate derivation: amount of substance vs concentration [closed]
Let's say you have the reaction
$$A + B \; \rightarrow \; C.$$
I would like to understand why $\frac{\mathrm{d}[C]}{\mathrm{d}t}$ is proportional to $[A][B]$. I can see why
$$\frac{\mathrm{d}n_C}{\...
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Difference between pre-equilibrium and steady-state approximation?
Both are reaction mechanisms in which there are several steps and at least one intermediate present. However, I am confused about the differences of both methods, especially when using them to ...
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How to find the average half life of radioactive nuclide which undergoes two different decays?
Find the average life of a radio nuclide which decays by parallel paths,
\begin{align}
A &\rightarrow B\\
2A &\rightarrow B,
\end{align}
where the decay constants are $\lambda_1 = \pu{0....
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Using a Chi-Square distribution table to calculate fraction of gas molecules with activation energy
I couldn't decide whether to ask this to Chemistry, Physics or Statistics stack exchange. Hopefully I made the right choice.
According to this Wikipedia page, while the speed of particles in an ideal ...
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Order of reaction for hydrogen ions being ignored
I have been reading through a case study about calculating the order of reaction for the following reaction:
$$\ce{H2O2 + 3 I- + 2 H+ -> I3- + 2 H2O}$$
The paper uses an iodine clock reaction ...
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How to find the time elapsed in a second order reaction given the final concentration?
This is an example in my textbook that I am trying to figure out
$$1/[\ce{A}] = 1/[\ce{A}]_0 + kt$$
In this case:
\begin{align}
[\ce{A}] &= \pu{4.62E-2 M}\\
[\ce{A}]_0 &= \pu{0.217 M}\\
k &...
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Rate of Reaction and half life [duplicate]
During the course of chemical kinetics while studying zero order or first order they consider rate of reaction to be dependent only on single Reactant
For ex:- A--> product,Rate of Reaction=k[A]^0 ...
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The differential rate law applies to only one single species
In my book it was written that
The differential rate law applies to only one single species, so unless we have equimolar amounts of each reactant or make an approximation using an excess of one, we ...
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Can a non-rate determining step control what products form in a reaction?
In Organic Chemistry by Clayden, the stereoselectivity and regioselectivity of the E1 mechanism is explained in terms of the differing transition state energies (and therefore rates) of the possible ...
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Reversible monomolecular reaction with two reverse rates
I think this is a simple problem but my kinetics are terrible and I was hoping for some assistance following up on the work of a previous student. I'm open to any form of assistance and I hope this ...
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Calculating rate constant for reaction between ethyl acetate and sodium hydroxide
My research question is investigating how temperature affects the rate constant for the reaction between ethyl ethanoate (acetate) and sodium hydroxide. I understand that I must titrate sodium ...
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