Questions tagged [kinetics]
The study of rates and steps in mechanisms of chemical processes.
727 questions
0
votes
1answer
34 views
Relation between activation energy and rate constant
Consider two types of reaction. One has more activation than other. If we increasing temperature by same amount in both, rate constant of which reaction will increase more?
My attempt: as we know ...
0
votes
0answers
45 views
Which of the following statements is true if HI is formed in the following reaction?
Which of the following statements is true if HI is formed in the following reaction?
$$\ce{H2(g) + I2(g) -> 2HI(g)}$$
a. There are no collisions between the reactants in the reaction.
...
0
votes
0answers
30 views
intuitive explanation of Wegscheider condition and its violation
The Wegscheider condition restricts the values that rate constants in a set of chemical reactions can take on. can someone please explain intuitively why the condition has to be true, and give a ...
1
vote
1answer
46 views
What does it mean for chemical reaction network to be in equilibrium?
What does being in "equilibrium" mean for a set of chemical reactions? If we have some number $n$ of $\ce{A}$ molecules and $m$ of $\ce{B},$ and the following reaction where $\ce{A}$ and $\ce{B}$ can ...
9
votes
1answer
265 views
+50
Understanding Kolomogorov backward equations in active biological systems?
I am trying to understand the following equation from the paper by Wang et al. [1, p. 5 at the SI]:
Michaelis–Menten Representation of the Kinesin Cycle
We assumed that there is a strong ...
0
votes
0answers
30 views
Robinson annulation
In the mechanism of Robinson annulation, what is the rate determining step?
I have searched in my book but it is not given. If possible please specify the reason for that step being the RDS.
Thanks in ...
6
votes
1answer
81 views
Equilibrium constant for a solid-solid equilibrium
Suppose there are two equations:
$$
\begin{align}
\ce{A(s) &<=> B(g) + C(s)} &\quad &K_1 \tag{R1}\\
\ce{B(g) &<=> D(s) + E(s)} &\quad &K_2 \tag{R2}
\end{align}$$
...
1
vote
0answers
39 views
Reactivity of Grignard reagent
I had the following question at an exam:
What is the fastest reacting compound towards nucleophilic addition with Grignard reagent?
(a) Acyl chloride
(b) Aldehyde
(c) Ester
It is ...
5
votes
2answers
128 views
Derivation of time probability distributions for single molecule kinetics
If we have a protein $\ce{A}$ that can bind to protein $\ce{B}$:
$$\ce{A + B <=>[$k_\mathrm{fwd,1}$][$k_\mathrm{rev,1}$] AB}$$
and the bound complex $\ce{AB}$ can be converted into $\ce{C}$:
$...
0
votes
0answers
26 views
Rate of reaction
For a reaction say
$$\ce{nA->B}$$ with $$\text{rate} =k[A]^n$$
So do we write rate as $ \frac {-\mathrm d[A]}{\mathrm dt}$ or $\frac{1}{n} \frac {-\mathrm d[A]}{\mathrm dt}$ We have only been ...
0
votes
1answer
45 views
Is activation energy time-dependent?
I was thinking lately about activation energy's dependency on time. I couldn't find any information on the internet. Only answer that came up to my mind is the fact that activation energy is constant, ...
0
votes
1answer
38 views
Microscopic and mechanical approach to boiling point [duplicate]
I am confused as to how I should visualize the boiling process throughout a liquid.
From my understanding, the boiling point of a liquid is when its vapor pressure reaches atmospheric pressure. This ...
1
vote
2answers
48 views
Rate law of the reaction of propane with oxygen
In class, I have a demonstration where I light a bubble filled with propane. As I add oxygen, the bubbles combust faster and more quickly. I have already balanced out the chemical reaction like so:
$$...
3
votes
1answer
68 views
Distribution of polymer lengths
Suppose we have a chemical reaction where a linear chain can form (reversibly) from building blocks (e.g. atoms or molecules):
$$\ce{X_$i$ + X_$k$ <=>[$k_\mathrm{fwd}$][$k_\mathrm{rev}$] X_$i$...
0
votes
0answers
13 views
Where can I find equilibrium constants for a specific reaction? [duplicate]
I'm doing a project on the production of dap fertilizer, but I can not find a database with kinetics constants(reaction rate constant.)
It's based on TVA Process for production of granular diammonium ...
4
votes
2answers
52 views
Y-axis of the reaction co-ordinate graph
In the graph of the reaction co-ordinate, is the $y$-axis that is used $∆H,$ $∆U$ or $∆G$?
1
vote
1answer
67 views
Why does the rate of the reaction decrease with an increase in temperature?
Why does the following reaction
$$\ce{2NO + O_2 -> 2NO_2}$$
have negative reaction coefficient, i.e., why does the rate of the reaction decrease with an increase in temperature ?
I have been ...
1
vote
2answers
58 views
Implication of negative order on kinetics
In the reaction
$$\ce{2 O3 -> 3 O2}$$
the order of reaction that I have been taught is
$$\ce{O_3 \underset{$k_{-1}$}{\overset{$k_{1}$}{<=>}} O_2 + O}$$
$$\ce{O_3 + O \overset{$k_{2}$}{->...
1
vote
0answers
27 views
Why is the nucleophilic substitution of OH- with 1-bromopentane slower than with 2-bromo-2-methylbutane?
Which statement about the reaction of a hydroxide ion with the organic reagent is correct?
A. 1-bromopentane predominantly follows an $\mathrm{S_N1}$ mechanism.
B. 2-bromo-2-methylbutane ...
0
votes
0answers
27 views
Do all zero order reactions occur as combination of multiple elementary reactions?
In a reaction, the rate determining step (RDS) gives the order of reaction. There might be 2 or 3 molecules colliding to give a product (2nd or 3rd order) or a molecule breaks for order 1. But for ...
2
votes
0answers
38 views
Gibbs free energy of activation and activation energy [duplicate]
What the difference between Gibbs free energy of activation and activation energy
1
vote
1answer
43 views
Equilibrium constant for a multi-step reaction [closed]
If a reaction proceeds in steps, is the equilibrium constant of every step taken into account to arrive at the final constant? Or can we just calculate equilibrium constant for the overall reaction ...
1
vote
0answers
31 views
Reaction Mechanism with a Rate Determining Step
Just a quick question on how to deal with multiple intermediaries in a proposed reaction mechanism.
Here is the overall reaction:
$$\ce{I-(aq) + OCl-(aq) -> IO-(aq) + Cl-(aq)}$$
Here is the ...
0
votes
0answers
31 views
First order reaction
I am little bit confuse about relating the half life time period of a first order reaction something like
$$\ce{2A -> B + C}$$
Here the rate of reaction will be half of the rate at which $\ce{A}$ ...
0
votes
1answer
32 views
Organic reaction rate equations needed [closed]
Where to find a list of common organic reaction rate laws?? Anybody has this?? I could not find one on internet
0
votes
1answer
28 views
Which of the following procedures will allow the student to determine the rate constant, for the reaction? [closed]
Is the answer A or B because C and D won't give me the rate constant?
1
vote
1answer
48 views
SN1, SN2 and enantiomeric excess
When (R)-2-bromobutane is heated with water, the $\mathrm{S_N1}$ substitution proceeds twice as fast as $\mathrm{S_N2}$. Calculate the appropriate enantiomeric excess and the specific rotation of the ...
1
vote
0answers
39 views
Plotting the Arrhenius curve without the rate constant
I was carrying out an experiment about finding the activation energy of the Maillard reaction using the Arrhenius equation. Since I didn't know the rate constant for the reaction due to the complex ...
2
votes
2answers
165 views
Why the concentration with respect to time equation of a first-order reaction does not depend on the stoichiometric coefficient of reactant?
According to my Chemistry textbook (Chemistry by Raymond Chang 10th edition, pg 570), for a first-order reaction of the type $$\ce{A->product}$$
the rate is $$rate=-\frac{[\Delta A]}{\Delta t}$$
...
1
vote
1answer
33 views
Rate expression for the final product [closed]
Let's say we have:
$$
\begin{align}
\ce{A &-> B}&\quad&\text{(fast equilibrium)}\label{rxn:1}\tag{1}\\
\ce{2 B + C &-> D}&\quad&\text{(slow)}\label{rxn:2}\tag{2}\\
\...
0
votes
1answer
22 views
Which is better: Increase in collision frequency or increase collision energy
What would have a greater effect on the rate of a reaction, increasing the frequency of collisions or increasing the collision energy of the particles? (assuming that using a catalyst is not an option)...
10
votes
0answers
132 views
What happens when para-water ice is suddenly melted?
Background (hydrogen)
In the case of recently liquified hydrogen (which is quite cold of course) it must be re-equilibrated before loading on to a rocket as fuel to avoid a sudden exothermic ...
0
votes
0answers
22 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 ...
0
votes
1answer
44 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 ...
1
vote
1answer
135 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
45 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
52 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
25 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
40 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
56 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?
0
votes
0answers
16 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
44 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
52 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 ...
0
votes
3answers
48 views
Effect of concentration on rate of reaction
I came across this problem:
The $\ce{2NO + Br2 -> 2NOBr}$ follows the mechanism below:
$$
\begin{align}
\ce{NO + Br2 &-> NOBr2} & &\text{fast} \tag{1} \\
\ce{NO + NOBr2 &-...
0
votes
0answers
19 views
What are the activation energies for the combustion of RP-1 with liquid oxygen, and UDMH with Dinitrogen tetroxide?
I need to compare the chemical and physical properties of the two reactions for a school project. However, I can't find a source that explicitly states their activation energies! We haven't learned ...
1
vote
2answers
97 views
Determining Kc for the equilibrium involving iron thiocyanate using spectrophotometric data
$$\ce{Fe^3+(aq) + SCN-(aq) <=> [Fe(SCN)]^2+(aq)}$$
$\pu{12.0 mL}$ of $\pu{0.00110 mol L-1}$ $\ce{Fe^3+}$ was added to $\pu{6.00 mL}$ of $\pu{0.00140 mol L-1}$ $\ce{SCN-}$. The absorbance of ...
0
votes
0answers
38 views
Equilibrium Constant and Reaction Mechanism [duplicate]
How is it possible for the equilibrium constant to not depend on a reaction's mechanism?
For the elementary reaction
$$aA + bB \rightleftharpoons dD + eE$$
I understand that the rate of the ...
2
votes
0answers
95 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
32 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
82 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 ...
