Questions tagged [kinetics]
The study of rates and steps in mechanisms of chemical processes.
-2
votes
0answers
43 views
Find average rate of the reaction based on decrease of reactant's concentration
A reaction happens where $\ce{A}$ is converted into $\ce{B}$. It takes $\pu{4 min}$ for the concentration of reactant $\ce{A}$ to decrease from $\pu{3.0 M}$ to $\pu{1.0 M}$. What is the average rate ...
0
votes
0answers
7 views
Rate of nucleophilic addition reaction of carbonyl compounds
How should I compare the order of rate of
1.formaldehyde
2.ethanal
3.p-nitrobenzaldehyde
4.p-methoxybenzaldehyde
For nucleophilic addition the rate depends on the intensity of electron deficiency of ...
-2
votes
0answers
19 views
Order of acid-carbonate reactions [on hold]
For an assignment I am investigating the reaction
$$\ce{MCO3 + 2HCl -> H2O + CO2 + MCl2}$$ where M is a group 2 metal and zinc. I am investigating changes in the rate of reaction and for that I ...
0
votes
1answer
39 views
2-step reaction mechanism for the decomposition of NO2Br
I need to propose a 2-step reaction mechanism for the following reaction:
$$\ce{2NO2Br -> 2NO2 +Br}$$
And prove the mechanism is consistent with: $$v=k[\ce{NO2Br}]^2$$
For the mechanism to be ...
0
votes
1answer
44 views
Rate of hydrolysis of ester in presence of an acidic medium
Does the rate of hydrolysis of an ester depend on the concentration of both the ester and the acid, or only the ester?
I was told by my professor that hydrolysis of ester follows a pseudo-first order ...
0
votes
1answer
33 views
Relationship between rate of reaction and pressure
Given the equation
$$\ce{A(g) + B(g) → C(g) + D(g)}$$
with reaction rate given by
$$v = k[\ce{A}]^2$$
How can I prove that reaction rate goes up with pressure? I tried substituting $k$ for $Ae^{-...
1
vote
1answer
44 views
Which is more stable in gas phase, free radicals or ions?
Answering some kinetics questions I came across this statement:
Free radicals are more stable in the gas phase than ions.
Is this correct or not? Why? Is there a different trend in liquid or ...
0
votes
0answers
22 views
SpectroVis spectrophotometer values changing after pulling cuvette out
I am required to write a research paper for school in a specific subject and I have chosen to write mine in chemistry.
I am investigating the kinetics of the Briggs-Rauscher oscillating reaction.
I am ...
0
votes
1answer
34 views
Calorimetry: Temperature Increase due to stirring of reactants
I am not yet in university, but I hear a common first-year chemistry lab/practical is to do calorimetry taking into consideration the small (and usually negligible) rise in temperature due to the ...
0
votes
1answer
33 views
Sulphonation of benzene
Will nitrobenzene and benzene have the same rate towards sulphonation reaction, since the formation of sigma complex is not the RDS of this reaction?
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votes
0answers
21 views
Rate order of a reactant based on graph
An irreversible reaction A + B products is studied under conditions where the initial concentrations of A and B are equal. Under these circumstances, a graph of ln([A]) as a function of time is ...
0
votes
0answers
11 views
Kinetics for E1cb reactions
We were taught that the kinetics of a reaction is determined by the reactions ‘rate determining step’ which is also the slowest step of the reaction. For E1 as well as E2 reactions the slowest steps ...
3
votes
1answer
32 views
Taking kinetic readings for the Briggs–Rauscher oscillating reaction
I am current doing the IB diploma program where we are required to do an extended essay which is a form of a research paper on a specific subject. I chose chemistry.
I am analysing the kinetics of ...
2
votes
3answers
41 views
Changing the order of the reaction with change in concentration
The reaction
$$\ce{2 A + B + C -> D + 2 E}$$
is found to follow the rate law as
$$r = k[\ce{A}][\ce{B}]^2[\ce{C}]^0$$
If the concentration of $\ce{A}$, $\ce{B}$ and $\ce{C}$ increases two times ...
-1
votes
0answers
24 views
What is the expected product of reaction between PCC and NAC that has an lambda max at 255nm?
250 nm and 214 nm are the maximum wavelengths of n-acetyl cysteine disulfide according to this paper "On N-acetylcysteine. Part 11. Oxidation of N- acetylcysteine by hydrogen peroxide: a kinetic study ...
0
votes
3answers
44 views
Effect of concentration on rate of reaction
I came across this problem:
The $\ce{2NO + Br2 -> 2NOBr}$ follows the mechanism below:
$$
\begin{align}
\ce{NO + Br2 &-> NOBr2} & &\text{fast} \tag{1} \\
\ce{NO + NOBr2 &-...
0
votes
0answers
18 views
What are the activation energies for the combustion of RP-1 with liquid oxygen, and UDMH with Dinitrogen tetroxide?
I need to compare the chemical and physical properties of the two reactions for a school project. However, I can't find a source that explicitly states their activation energies! We haven't learned ...
1
vote
2answers
52 views
Determining Kc for the equilibrium involving iron thiocyanate using spectrophotometric data
$$\ce{Fe^3+(aq) + SCN-(aq) <=> [Fe(SCN)]^2+(aq)}$$
$\pu{12.0 mL}$ of $\pu{0.00110 mol L-1}$ $\ce{Fe^3+}$ was added to $\pu{6.00 mL}$ of $\pu{0.00140 mol L-1}$ $\ce{SCN-}$. The absorbance of ...
0
votes
0answers
37 views
Equilibrium Constant and Reaction Mechanism [duplicate]
How is it possible for the equilibrium constant to not depend on a reaction's mechanism?
For the elementary reaction
$$aA + bB \rightleftharpoons dD + eE$$
I understand that the rate of the ...
2
votes
0answers
53 views
Kinetic and thermodynamic control of sulphonation of toluene
Sulfonation of toluene with conc. $\ce{H2SO4}$ at room temperature gives ortho- and para-toluenesulphonic acid (with $95 \%$ yield), whereas sulfonation of toluene with conc. $\ce{H2SO4}$ at $\pu{150-...
2
votes
1answer
26 views
Pseudoelementary reactions in the Briggs-Rauscher oscillatory reaction mechanism
In this paper on the Briggs-Rauscher mechanism (JACS, 1982, paywalled), Noyes and Furrow propose an explanation of the oscillatory behaviour of the reaction based off of about eleven reactions from a ...
3
votes
0answers
37 views
Calculating pre-exponential factor using transition state theory
I would like to calculate the pre-exponential factor of a surface reaction using transition state theory. I've seen two ways to calculate it but I get different answers for each method (and I don't ...
1
vote
0answers
14 views
How to define the reduced mass for estimating Kinetic Isotope Effects
I am trying to think about radical reactions using zero-point energies (from the harmonic oscillator model). I have read that substitution of a bond with isotopes can alter the rate of a reaction.
...
5
votes
2answers
53 views
Intuition for why catalyst affects both forward and reverse reactions equally?
I have looked for quite a long time on the site however all the answers involve mathematical explanations involving Arrhenius's equation. I would really like an intuitive reason (or one using ...
1
vote
0answers
15 views
Finding Pressure of M in a Charge Exchange
Ar (RE = 15.5 eV) is the reagent gas in a charge exchange experiment. If Ar+ reacts with anisole with a rate constant of 2.26x10-10cm3 molecules-1/s-1 and 65% of the Ar ions react in 25 milliseconds, ...
1
vote
0answers
24 views
Kinetic Shift of Simple Cleavage
What is the kinetic shift for the simple cleavage fragmentation if the ion source residence time is 100 microseconds, the time to reach the detector after leaving the ion source is 10 microseconds? (...
1
vote
0answers
18 views
Is the iodide and persulfate reaction bimolecular?
Given the following reaction in an aqueous state:
$$ \mathrm{2I^- + S_2O_8^{-2}\rightarrow I_2 + 2SO_4^{2-}}$$
Is it bimolecular o trimolecular? Because two molecules of iodide react with one ...
0
votes
1answer
48 views
how to calculate the initial concentration of NaOH in a mixture? [closed]
I have doubts about how to find the equation for the calculation of the initial concentration of $\ce{NaOH}$. I have the following information:
in the kinetic study of a reaction,
We measure $\ce{20....
13
votes
2answers
897 views
Is there a difference between equilibrium and steady state?
The term equilibrium is used in the context of reversible reactions that reach a point where concentrations no longer change. The term steady-state is used in enzyme kinetics when the concentration of ...
0
votes
2answers
71 views
Why is the rate of reaction calculated as d[A]/dt?
For example, for a simple chemical reaction like
$$\ce{A -> C}$$
the rate of the reaction could be calculated as the rate of appearance of $\ce{C}$ or the disappearance of $\ce{A}$, which makes ...
1
vote
2answers
93 views
How to determine steady state of multi-step reaction with both reversible and irreversible steps?
I am trying to determine the relative concentrations of $\ce{U1}$, $\ce{U2}$, and $\ce{E}$ when the following reaction is at steady state. Note that $k_t$ is the zero order rate constant of new $\ce{...
3
votes
0answers
71 views
Kinetic model of proton reduction
One of my colleagues is working on a homogeneous catalyst ($\ce{X}$) for proton reduction. The simplified proposed mechanism for it is the following.
$$\ce{X + 2 e^- ->[$k_1$] X^{2-}} \tag{1}$$
...
3
votes
1answer
95 views
Why we should concern with A∞?
To determine the order of one reactant at pseudo concentration of another reactant the plot of $\ln(A_t - A_∞)$ versus $t$ is used.
$A_t$ is absorbance of the intermediate at time $t$.
$A_∞$ is ...
1
vote
2answers
101 views
Denominator in rate law?
What the possible rate laws are for the decomposition of nitramide by the following process:
$$
\begin{align}
\ce{O2NNH2(aq) &<=>[$k_1$][$k_{-1}$] O2NNH-(aq) + H+(aq)} &\quad &\...
2
votes
1answer
76 views
Determining reaction order in equilibrium reactions [closed]
Am hoping that someone can help me with the below question, and that I am asking in the right place. Am new here, so please forgive any missteps.
Given a reaction like this:
$$\ce{A + B <=> C +...
2
votes
2answers
54 views
Measuring a high Michaelis constant using fluorescence
We have the task of measuring kinetic parameters of an oxidase reaction that has a $K_M$ of about $2 \,\text{mM}$. For that, we want to use a fluorescence assay based on Amplex Red. The latter is a ...
0
votes
1answer
40 views
Rate of change of reaction rate of 0th, 1st, 2nd order reaction?
Does the rate of change of the reaction rate for a 1st order reaction change linearly over time? My teacher says it does, but my textbook seems to contradict this. Could anyone clarify?
0
votes
1answer
124 views
what the solution of this problem, negative absorbance values in UV-vis spectrum
In my project, I take the UV-visible spectrum of reaction between pyridinium chlorochromate and N-acetylcysteine. In some wavelengths, the absorbance value is negative for example it is (-0.006, -0....
0
votes
0answers
37 views
Using Maxwell–Boltzmann distribution in reacting systems
In the book Physical Chemistry, a Molecular Approach by Simon and McQuarrie, the have used the Maxwell–Boltzmann distribution for velocity of molecules to estimate the the rate constant of a reaction. ...
0
votes
1answer
38 views
Inactivation of enzyme: Why inactivation constants do not follow the Arrhenius equation? [closed]
The Arrhenius equation may not account for the temperature effect on thermal inactivation rate constants. Why can the thermal inactivation kinetics not be expected to follow Arrhenius? The reason that ...
0
votes
2answers
78 views
Rate law equation - orders?
Consider the following reaction:
$$\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{...
11
votes
2answers
248 views
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,
$$ k = A \exp\left(-\frac{E_\mathrm ...
1
vote
2answers
62 views
Which rate, the forward or reverse rate of acid dissociation, is more strongly affected when diluting acetic acid in aqueous solution?
Acetic acid is a weak acid. It is in equilibrium with acetate and hydronium ions in aqueous solution:
$$\ce{CH3COOH(aq) + H2O(l) <=> CH3COO-(aq) + H3O+(aq)}$$
Ostwald's law states that the ...
0
votes
0answers
15 views
Does the starting concentration in a isochoric container depend on the pressure?
Given is the following reaction of carbonic acid and carbon dioxide:
$$\ce{RCOOH (g) → RH (g) + CO2 (g)}$$
The reaction rate of this decarboxylation was measured in a container with constant volume ...
0
votes
1answer
23 views
Determining the concentration after half-life period
I was given the reaction
In diluted solution and with neutral pH, the reaction reacts according to a reaction velocity law of pseudo-1. order:
$$-\frac{dc_{DNPA}}{dt}=k_{obs},\quad k_{obs}=k\cdot c_{...
1
vote
1answer
111 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 ...
2
votes
1answer
66 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 $\pu{5e-6 mol}$ $\ce{FeCl3}$ ...
0
votes
2answers
65 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 $...
3
votes
1answer
34 views
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 ...
0
votes
0answers
46 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{\...
