Questions tagged [kinetics]
The study of rates and steps in mechanisms of chemical processes.
911
questions
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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: $$\ce{CH_3C(O)CH_2^- ...
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0answers
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How to learn the concept behind Thermodynamics, Equilibrium, Electrochemistry, Chemical Kinetics [closed]
I am currently reading Thermodynamics, Chemical Equilibrium, Ionic Equilibrium, Electrochemistry, Chemical Kinetics for JEE Advanced exam in India. Now when I am solving problems I can not inter ...
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1answer
56 views
Activity of Polonium in half-time in Becquerels
I got an exercise but I don't know the exact answer.
In the catalog note of the reference source of Polonium-210 radiation with a half-life of 138 days, it was stated that one day the activity was $\...
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0answers
9 views
Temperature change vs time in first order reaction [closed]
Please tell me how to write a formula for the variation of the temperature (T) as a function of time (t) and E. for a first-order reaction by linking it with Arrhenius equation and Eyring Equation as ...
3
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1answer
63 views
Why a catalyst is not consumed in a reaction when all steps are reversible?
It is said that a catalyst speeds up the rate of a reaction but is not consumed (assuming no side reactions take place). Suppose we have the following reaction:
$$\ce{A + B <=> C} $$
catalysed ...
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0answers
12 views
Relation between Temperature from the Arrhenius equation of the first order reaction and the time taken by the reaction [closed]
Consider the chemical transformation of a gas A to a gas B:
π΄βπ΅ π»πππ‘ ππ πππππ‘πππ; Ξπ»π=β1000π½πππ, Ξππ=100π½ππππΎ.
The enthalpy and entropy of the reaction are temperature ...
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1answer
59 views
Equilibrium constant of a reaction whose order of forward and reverse reaction is not same
Suppose, a reaction is like,
$$\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}$$
Now if the forward reaction is second ...
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0answers
13 views
Is standard change in activation Gibbs free energy indepedent of pressure?
For a chemical reaction the activation volume is defined as:
$$Ξ^{\ddagger}V={V^\ddagger}-V$$
where both $V^\ddagger$ and $V$ refer to standard states (I have omitted the symbol for simplicity). One ...
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1answer
22 views
kinetic description of an autocatalytic system
I have previously asked this question at physics SE here and it was suggested to post it here.
I am looking at the system:
$2X + Y \Leftrightarrow 3X $
$A \rightarrow Y$
$X \rightarrow B$
The ...
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0answers
18 views
adiabatic reversible process problem
A compressor recieved air at To= 300 K and at pressure Po= 1 atm. At the exit, P1 = 2 atm. The process inside the compressor is (A) adiabatic and reversible (B) gas is an ideal gas (3) gamma = Cp/Cv = ...
1
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1answer
36 views
Why are the “extents of reaction” the same for all reactants and products?
Consider the follwoing reaction:
$$\ce{a A + b B -> c C + d D}\tag{1}$$
where $\ce A$ and $\ce B$ are the reactants, $\ce C$ and $\ce D$ are the products, and $a (<0)$, $b(<0)$, $c(>0)$, ...
1
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1answer
50 views
New relationship between exponential factors and entropy of a reaction?
Consider the reaction $\ce{A <=> B}$. Let $k_f$, $E_A$, and $A$ denote the forwards rate constant, activation energy, and pre exponential factor, respectively. Let $k_r$, $E_A'$, and $A'$ denote ...
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11 views
Reversible equation in Chemical Kinetics β Should I use definite integral when solving the differential equation?
I found this problem:
We have the following reversible reaction: $A \ce{<=>[\ce{k_1}][\ce{k_2}]} B $, described by the kinetics equation:
$$\frac{d[X]}{dt} = k_1([A]_0-[X])-k_2([B]_0+[X])$$
...
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0answers
46 views
Getting close to zero percent of particles with energy greater than an activation energy of 101kJ/mol using the Maxwell-Boltzmann energy distribution
I experimentally obtained the activation energy of a reaction to be approximately 101kJ/mol. I was then going to use the value for the activation energy to see how the number of particles with ...
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0answers
22 views
Receptor and Ligand Binding
Hope this is the right place to ask.
I'm reading chp. 2 of 'Receptors, models for binding, trafficking, and signaling' by Lauffenburger.
In it they describe a situation where there are ligands that ...
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0answers
30 views
Determine the rate law for the given reaction
I was studying for a PhD entrance exam and this question made me wonder about some topics in kinetics:
Consider the multi-step reaction below:
$\ce{A_2 β 2 A}$
$\ce{2A + X β Y + B}$
$\ce{B β A2 + Z}$
...
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1answer
37 views
Relationship between molecularity and the reaction order
Should the molecularity be equal or less than the reaction order?
Consider the reaction:
$$\ce{H2(g) + I2(g) β 2 HI(g)}$$
If we consider the mechanism of this multi-step reaction, the molecularity is ...
2
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1answer
39 views
Frequency Factor of the Arrhenius Equation
The question came to my mind as to whether the effect of a catalyst on a reaction included the modification of the frequency factor (or pre-exponential factor) of a reaction, shown in Arrhenius' ...
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0answers
40 views
Concentration and rate constant
E.g. for a first-order reaction, rate of reaction = k[A], I can see that a higher concentration of A leads to a higher rate due to an increased chance of effective collision.
According to this, ...
1
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1answer
69 views
Activation energy and degrees of freedom
According to the Arrhenius equation the rate of a reaction increases as at higher temperature a greater percentage of molecules have translational kinetic energy greater than or equal to activation ...
1
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1answer
22 views
Rate of change and kinetics order of reaction question
The rate of reaction is given by the following equation, where [Ker-S-S-Ker] is just the molecule being broken down and [RSH] is an abbreviation for thioglycolic acid
The thioglycolate is in large ...
2
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0answers
38 views
Concentration of sulfur in turbid solution
I recently participated in an experiment where I need to calculated the reaction orders and the reaction constant of the reaction:
$$\ce{8 Na2S2O3(aq) + 16 HCl(aq) -> S8(s) + 8 SO2(g) + 16 NaCl(aq) ...
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0answers
29 views
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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30 views
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 ...
3
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1answer
49 views
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,
$$\ce{O3 + M <=>[$k_1$][$k_{-1}$] O2 + O + M}...
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4answers
59 views
Confusion over the rate law
I am really confused about the rate law. From my understanding, the rate law gives an equation that tells us the rate of the disappearance of the reactants. So, for example, the rate law of the ...
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0answers
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Determine the order of reaction [duplicate]
Is there any formula that can help determine the order of the reaction?
Cause my teacher told me to plot line chart. So, I am curious about another method that doesn't use line chart (like formula ...
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2answers
41 views
Can rate constant depend upon the concentration of reactants (or other species involved in the reaction)?
Transition state theory tells us that the rate constant of an elementary step is $$\ce{k_r=\frac{\kappa k_BT}{h}e^\frac{- \Delta G^\ddagger}{RT}}$$
where $\ce{\Delta G^\ddagger}$ is the activation ...
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1answer
769 views
Why is a third body needed in the recombination of two hydrogen atoms?
In the article Discuss. Faraday Soc. 1962, 33, 205, the authors say that in order to form molecular
hydrogen from collision to atom we need a third body to remove the excess energy. That is we have ...
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35 views
Rate expression with water as one of the reactants
When finding an equation for d[A]/dt from reaction mechanisms and $\ce{H2O}$ is a product/reactant, does $\ce{H2O}$ have to be included or left out like for equilibrium constant expressions?
For ...
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Is order defined for a reaction which does not follow power law dependence?
As per my knowledge , order of a reaction is the sum of exponents of all the terms in rate law of the reaction
But reaction which do not follow power law dependence , for example , formation of HBr , ...
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35 views
Parallel reactions for one product
For me it is clear how I could solved the kinetic of a parallel reaction like this
But, how can I solve if this would be the case:
Thanks in advance!
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2answers
45 views
Organic-catalysis microwaves [closed]
When we perform a organic reaction without any addtional catalyst except that the reaction is carried out under microwave condition we can accelerate this reaction in comparison with one under heating ...
2
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1answer
61 views
Rate law for A + B β C β P
I need some clarification for the following assignment:
Derive the rate law for
$$\ce{A + B -> C -> P}$$
when $\ce{A + B -> C}$ is the slowest step and very slow.
My understanding is $\ce{A ...
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1answer
37 views
How does it affect the equilibrium expression if the concentration of any component remains the same?
I am a high school student and I am very confused in Equilibrium expression, My confusion is that "Why we don't write concentration of solids and pure liquids in equilibrium expression?" ...
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Is this statement valid for reactions of all orders? [duplicate]
My textbook (not an international standard) states that for the first order reactions only
The quantity of reactant remaining after $n$ half lives is
$$A_n = \frac{A_0}{2^n},$$
where $A_0$ is the ...
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0answers
34 views
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 ...
2
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1answer
29 views
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 ...
1
vote
2answers
49 views
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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0answers
28 views
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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1answer
21 views
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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1answer
66 views
Wikiβs explanation of the rate of chemical reaction [closed]
Could you please help me understand the Wikiβs 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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5answers
983 views
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 ...
1
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1answer
62 views
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$$
I want to estimate the pre-exponential factor of this ...
0
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1answer
89 views
Why does activation energy depend on temperature? [duplicate]
To me it makes sense that the activation energy $E_\mathrm a$, as given by the Arrhenius equation, doesn't depend on the temperature as the needed energy (potential energy) to start a reaction has ...
2
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1answer
143 views
Kinetics question regarding Rate Law
The acid catalysed hydrolysis of an compound $\ce{A}$ at $\pu{303K}$:
$$\ce {A ->[$k$] B}$$ has a half-life of $\pu{100 min}$ when carried out in a buffer solution of $\mathrm{pH=5}$ and $\pu{10 ...
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116 views
Deriving an expression for reaction time in terms of the total concentration
Consider the dimerization of protein $\ce{A}:$
$$\ce{2A <=> A2}$$
with forward rate constant $k_1$ and backwards rate constant $k_{-1}.$ Derive the following expression for the reaction time in ...
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0answers
43 views
Kinetics of Decomposition of Hydrogen Peroxide [duplicate]
Consider the decomposition of Hydrogen Peroxide:
$$\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}]}...
2
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0answers
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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-...
