Questions tagged [kinetics]
The study of rates and steps in mechanisms of chemical processes.
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0answers
19 views
Half life of A in the first order reaction 2A+B-> Products [on hold]
In the reaction 2A+B->Products, if Rate=k[A] and k=0.0693 then what is the time taken to consume half of A?
Can someone please provide a solution to this question?
Regards,
Apoorv
0
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2answers
54 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 $...
1
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0answers
11 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
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0answers
43 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{\...
1
vote
1answer
40 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 ...
6
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0answers
51 views
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:
...
0
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0answers
31 views
Measuring activation energy without changing temperature
Does anybody have an alternative approach to finding activation energy of a reaction without using Arrhenius plot?
Using Arrhenius method involves changing temperature at which the reaction occurs ...
6
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1answer
43 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 ...
1
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0answers
43 views
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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1answer
51 views
Find order of reaction with respect to A and B and find the rate law expression for 2A+B -> C [closed]
Please help me in this chemistry question
2
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1answer
43 views
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
32 views
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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0answers
36 views
How do acids disassociate? [duplicate]
When recently learning about acids and bases, I realized that I had perhaps not understood how it is that acids disassociate. I had always thought the proccess was like an ionic salt, where the water ...
1
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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 ...
0
votes
1answer
28 views
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 ...
0
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0answers
27 views
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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votes
1answer
53 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 ...
1
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2answers
33 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{...
2
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2answers
60 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
21 views
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 ...
7
votes
1answer
147 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 ...
0
votes
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? ...
0
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2answers
43 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 ...
0
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1answer
66 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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votes
1answer
35 views
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.
...
0
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1answer
28 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
34 views
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 ...
1
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0answers
49 views
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-...
0
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0answers
55 views
Observed activation energy of parallel and sequential reactions
I saw this sentence in a test:
Observed activation energy, $E_\mathrm{obs}$, increases with increasing temperature for parallel reactions and decreases with increasing temperature for sequential ...
1
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1answer
40 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, \...
1
vote
1answer
366 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 ...
2
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0answers
52 views
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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2answers
71 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:
$$[\ce{C}] = {1 - \exp(...
1
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0answers
31 views
A doubt regarding coefficients in rate law expression
For example, for the reaction $\ce{A + 2B -> C}$, we have
$$\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.$$ Together, ...
0
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1answer
43 views
Current in a Lithium Ion Battery
I am trying to find the current transferred to the anode and cathode of a Lithium Ion Battery at different voltages. I know the temperature (approximately) of the battery, the battery's starting ...
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1answer
42 views
Rate of a reaction [duplicate]
We know that the rate of a reaction $\ce{aA + bB -> cC + dD}$, the rate of the forward reaction is given by $r_\mathrm f = k_\mathrm f[\ce A]^p[\ce B]^q$ where $ a\neq p$ and $ b\neq q$ according ...
0
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1answer
29 views
Is it possible to apply reaction progress kinetic analysis on non catalytic reactions?
I was wondering if anyone familiar with reaction progress kinetic analysis knows if it is possible to apply the method on non catalytic reactions, and if so provide a few references with relevant ...
2
votes
1answer
119 views
What is 'power law' kinetics?
I've come across a lot of instances where 'power law' description of the kinetics was mentioned, but I cannot think of any integrated rate law that follows something like:
$$A(t)=bt^n+c$$
I'm pretty ...
5
votes
2answers
102 views
When are transition state's energy barrier “reasonable” at a certain temperature?
Every computational chemist who does a little bit of mechanistic studies has asked himself this question. When you obtain your first transition state and look at the activation barrier needed to ...
4
votes
2answers
310 views
Does the rate constant depend on pressure?
I have read in some books that when pressure increases, the number of effective collisions increases. Hence, $k$ depends on pressure. Is it true? If so, then why doesn't $k$ depends on concentration? ...
1
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0answers
37 views
Order of a complex reaction [duplicate]
Is the order of a complex reaction determined by the slowest step always? Is it so that order of a reaction is determined by rate determining step and since in a complex mechanism, we write elementary ...
4
votes
3answers
118 views
In regard to collision theory, why do molecules have to have the correct orientation in order to react?
Hypothetically speaking, if a reagent in a bimolecular reaction has enough energy to break the bond of the other reagent but is orientated in the wrong direction, why does the bond not break? Does the ...
1
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0answers
35 views
Does the ignition temperature of a substance decrease with the concentration of oxygen?
Is it possible for a substance to undergo combustion at a temperature lower than its ignition point if the concentration of oxygen increases?
0
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1answer
80 views
Parallel first order reaction
I am not able to solve this question. Here's my working
Have I done this in the right way? Because my textbook gives answer as 4 moles
3
votes
1answer
338 views
Optical rotation in inversion of sucrose [closed]
In reading about the inversion of sucrose I came across the equation for the reaction rate constant below:
$$k = \left(\frac{2.303}{t}\right) \log\left[\frac{\alpha(0) - \alpha(\infty)}{\alpha(t) - \...
2
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1answer
124 views
What is 'desorption hysteresis'?
I am currently reading a paper titled "Polystyrene Nanoplastics-Enhanced Contaminant Transport: Role of Irreversible Adsorption in Glassy Polymeric Domain" (link here).
In the paper, the authors ...
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1answer
50 views
Special first order reactions [closed]
I am having trouble understanding the equations....how is concenteration of ester proportional to the volume of NaOH used and how is initial concentration proportional to difference in the Volume of ...
0
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1answer
51 views
Second order reaction cases [closed]
https://chem.libretexts.org/Textbook_Maps/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/Reaction_Rates/Second-Order_Reactions
...
6
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2answers
172 views
Why does a reaction take time? [closed]
A reaction in nature is, as we know, generally an interaction between the electron clouds of different atoms and nuclei. Why does this takes time?
1
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1answer
81 views
Change of first order rate constant with temperature [closed]
In the decomposition of $\ce{N2O5}$, the time taken to reduce the concentration of $\ce{N2O5}$ half of the original amount is 12 min at $\pu{50^\circ C}$, while 5 h at $\pu{25^\circ C}$ and 10 days at ...
