Science topics: ChemistryChemical Kinetics
Chemical Kinetics - Science topic
Prediction, assessments and studies on the composition of reaction mixtures as a function of time, to understand the processes that occur during a reaction, and to identify what controls its rate.
Questions related to Chemical Kinetics
How to optimize number of theoretical stages in reactive, rectifying and stripping section using sensitivity analysis tool in ASPEN Plus? what would be the independent variable and dependent variable? Kindly explain i am performing simulations on reactive distillation process.
These types of figures are required in reaction kinetics modeling work.
I wanted to know if there is such a possibility since I have observed quite little difference in qcal values in case of both PFO and PSO models.
Hello everyone. I need help from you because I need to develop a Pareto Chart applied in chemical kinetics through Minitab. Can you help me with this, please
Hi everybody. I have a question about study kinetics. So, I did electrolysis by dissolving organic compounds with aquades as a sample under acidic conditions with Na2SO4 as electrolyte, with additional H2O2 (Fenton reaction) using iron as anode and graphite as cathode. In discussing the study of kinetics, I found that if the kinetic graph that R2 close to one or almost linear is in pseudo-second order graph, what does this pseudo-second order mean? what does pseudo-second order actually mean? i was told that "the pseudo explains that something is involved but doesn't appear in the rate law, for example the solvent or there is usually the fraction of the reactant that matters" is that true? So, if what is meant by second order is that there are two reagents that have an effect in this case, for example H2O2 and Na2SO4, but in pseudo-second order something is involved but it doesn't appear, what is it? also, if you also know, what kind of reaction mechanism that produces the pseudo?
Thanks in advance
Can absorption isotherms be used for gas-liquid absorption processes?
I have calculated the equilibrium products of high-temperature gaseous reactions from thermodynamic calculations. Meanwhile, I am curious about determining the kinetics of those reactions. I checked various resources, however cannot find any information on the kinetics of the reactions given below:
CO2 <--> CO + O2
2CO <--> C + CO2
CO2 + CH4 <--> 2CO + 2H2
CH4 <--> C + 2H2
Can you please provide me the procedure or references where I can estimate the kinetics of those reactions? Many thanks!
i am trying to simulate methane combustion using species transport model in fluent with detailed GRI mech 3 mechanism but I get no combustion. i also patch the temperature to a high value.
Has anyone worked with Detailed methane-air combustion in Fluent?
Mentioned in the publication ''RANS simulations on combustion and emission characteristics of a premixed NH3/H2 swirling flame with reduced chemical kinetic mode''.
See scenario below:
You are monitoring a certain chemical reaction (browning) of a product stored at different temperatures over a certain period. When applying kinetics to determine the reaction order, sometimes you find that this reaction fits/obeys both reaction orders (zero- and first-order). When determining the activation energy using the Arrhenius equation ( ln k = ln A - Ea/RT), which rate constants (k) do you choose (zero - k0 or first - k1)? Can you apply both or is it always k0?
F0/F versus Concentration of Quencher is a straight line, but I am unable to calculate the binding constant and number of binding sites.
Moreover, what will be the unit of the binding constant? Is it necessary to take the molar concentration of quencher?
Hello! I have a problem with a reformer kinetic implemented in Aspen Plus. I have a PFR reactor that need to be closed with a recycle. In this recycle there is a very small amount of H2 that invalidate the kinetic and gives me error, this is because in the reaction rate expression, some terms are divided for the partial pressure of H2, and therefor being so small, is like dive everything for zero and that is causing problem in the converge.
Is anyone of you familiar with such problem? There is a way to "eliminate" a component from a stream is present below a certain amount?
I guess my question is quite simple: you know how for compressible CFD codes we have the Sod Shock tube problem that we can use as a benchmark. What if I now want to expand my code and add chemical reactions to it, what would be a good/similar test problem that I could use to validate how well my code runs?
I have planned to do kinetic studies of Dry (CO2) Reforming of Methane experimentally and theoretically for my developed Ni/CeX-Zr1-XO2. I went through some published papers, and they have shown the final kinetics equation based on different kinetic models, which is very difficult for me to understand and perform for my experiment. May I get help from any one of you in this regard or anybody willing to research collaboration with me in these regard?
Thank you in advance for your kind consideration and any valuable supports!
Hello, I'm studying metal-catalyzed reactions between oleic acid + oleylamine (amidation) and oleic acid + oleyl alcohol (esterification). I have a general sense that, all conditions being equal, amidation should be faster, perhaps due to the basicity of the amine, but that seems sort of vague and I'm trying to get a full understanding of what I should expect. Any help would be much appreciated. Thanks!
motivation components intrinsic motivation, self-efficiency, self-determination, career motivation, and grade motivation in learning chemical kinetics and equilibrium
I would like to validate my regression algorithm which calculates activation energy and pre-exponential factor from the TGA curve. It uses integral method (the exponential integral for resolving the right side of the equation):
d_alfa/alfa = -A/beta*exp(-E/R*T)dT
where alfa is the extent of mass loss, beta - heating rate, A - pre-exponential factor, E - activation energy.
I compared my results with literature TG curves but, the results differ slightly. I'm wondering if the error is caused by my calculation algorithm or uncertainty of A and E estimation is so high.
Could anyone provide a simple TG curve (one component, first-order order kinetics) and corresponding A, E, and beta - I believe that the data calculated would be the best because I should receive exactly the same A,E result during regression using my algorithm.
The following data are obtained in an enzyme catalyzed reaction: [S]x10^4(moldm^-3): 2.5, 5.0, 10.0, 15.0.
Then rox10^6(moldm^-3min^-1) : 2.2, 3.8, 5.9, 7.1.
Assuming Michaelis-Menten Kinetics, calculate:
Using the Lineweaver- Burk and Eadie method.
Given [E]o = 4.0x10^-6 mol/dm^3
1. rmax- maximum rate
2. Km- Michaelis Menten constant
3. [S]- concentration of substrate
4. ro- initial rate
Check the image for clarity.
I am looking to find a material (any type) that can offer me CO formation energy (> 2.0 eV) and NO formation energy ( < 0.5 eV) simultaneously. Secondly, how to confirm these formation energies experimentally? Your expert opinion in surface reaction, catalysis would be appreciated. Thanks
In what case would a reaction rate always show direct relation with activation energy or would it always be an inverse relation? Is it a indirect relation, inverse relation or both case can hold? (Please provide supporting resource, thank you).
Trying to elucidate a reaction pathway, I calculated the energies for different transition states possible for that reaction (computational chem. DFT). I found activation free energies ranging from 29 to 39 kcal/mol, and wanted to understand if all those transition states are possible in the reaction conditions that were used in previous papers. That is, given that this reaction is known to occur at around 355 K, is it possible to overcome those free energy barriers of 29 to 39 kcal/mol?
I know I can calculate the rate constant for a given temperature using the Eyring equation but I'm not sure how to relate the rate constant to the reaction "feasibility".
I wonder if the activation energy calculated based on the Arrhenius plot for a multi-step reaction is a sum of activation energies of elementary reactions or is a difference between energy of reactants and energy of the transition state with the highest energy (associated with the rate-limiting step). Maybe, it is something else?
What if the reaction rate goes down, while the calculated activation energy from Arrhenius plot decreases?
I have a reaction involving calcium phosphate at pH 6.80 in a complex system that dissociated at low temperatures (I use ionic calcium concentration), which overall is in a metastable state (not in equilibria). In details, I have calculated the order or reaction (first-order) and all the K (rate constant) using ionic calcium concentration as my C values, at different temperatures from 4 to 35C. It is known that calcium phosphate has inverse solubility and thus the rate constants are higher when temperature decreases. Therefore, is it possible to have negative activation energy (Ea) for such reaction? I read that is possible for reactions involving halogens and ozone.
I want to purify my insoluble organic compound from sodium chloride through washing.
I have done my first trial with distilled water having tds approx 44 p.p.m and the second with fresh ground water having tds approx 500 p.p.m.
The results differs in both trials.
So how t.d.s and hard minerals affects the solubility of sodium chloride in water?
how can i calculate the ratio of solubility based on water quality (t.d.s).
Suggestions are highly appreciated.
I have been working on developing a reduced kinetic mechanism for diesel-biodiesel-gasoline mixtures. I have reduced the detailed mechanisms of each individual fuel and combined them to form the final mechanism via Chemkin software.
However, throughout the combining procedure, the Chemkin software does not offer any options to specify a quota for each individual fuel before mixing, so, please kindly guide me on how can I define a specific fraction of each fuel in the final mechanism?
How to calculate Kinetic Parameters from (TGA,DSC,DTA,DTG) curve using Coats-Redfern?
I hope it will be a practical example with detailed steps, whether in Excel or Origin or any other program (entropy S, enthalpy H, G, A, K)
I am trying to do analysis of solid rocket motor with non equilibrium turbulent combustion based on Eddy-Dissipation concept. Before doing analysis, I need to have chemical reactions and chemical kinetics such as reaction rate. How can I get them on chemkin? My solid propellant consists of mainly ''hydroxy-terminated polybutadiene, ammonium perchlorate, and aluminum''. You can find list of chemical reactions in the picture that I have to find on chemkin.
It makes the plastic undesirable but is listed in procedure.
Influence of ligand on an heterogeneous catalyst surface reactivity
I need thermophysical and electrical oil properties to investigation of DC discharge in oil.
Are multicomponent mixture models effective and precise in such calculations? If yes, what MC-modells can You suggest?
Can somebody advice something?
Thank you a lot in advance!
Anyone knowing metamorphic geology would know the sequence of mudrock to gneiss transformation and its intermediate steps, including mica formation and growth (slate, phyllite, schist) and breakdown (gneiss) as metamorphic change intensifies. One may also refer to any standard petrogenetic grid to locate P-T curve for that transformation, since composition of gneiss lighter bands (plagioclase,...) and darker bands (pyroxene, amphibole...) are also commonly known. My questions are-
- Mica being phyllosilicates with layered structure, gain what kind of free-energy lowering advantage by growing normal to direction of maximum compression instead of being growing, say, in scattered or parallel to maximum compression direction? what are the chemical factors that affect the layer spacing?
- Similar question for generation of lamellar lighter and darker bands in Gneiss by decomposition of mica into feldspar and mafics (why layer instead of scattered blobs?). Why the free energy (magnitude and hence stability) of phyllosilicates drop at higher P/T and what is the molecular-level mechanism of this exsolution? how this transformation is different from and similar to eutectoid phase transition seen in metals? What are the factors that affect spacing of the layers (quantitatively?)
While surface roughness is an obvious factor, this is not what is exactly asked. Rather, periodic variation of exchange current density (of an electrode) with solution chemistry (of electrolyte) and crystal structure (of the metallic electrode) is asked, if any of these exist.
I am using finite difference method to discretize the parabolic equation (explicit method), but confused about the chemical reaction term. Solving the generic equation for i specie involves a couple of species in the kinetic reaction equation since it is reversible ( Ex: A+B <-->C ). What is the best way to conquer the complexity in this manner? should I go with separation method and solve diffusion and reaction term separately. I am not quit sure if it is applicable. Thanks in advance.
We are in need of some software with which we can use templates of chemical isotherms like Langmuir, Freudlich, BET and others, and also chemical kinetics to get k value, linear graphs, non linear graphs, etc.
Literature is available and I am searching for a software or preprogrammed software (Exel/origin/others) along with templates with which I can draw graphs for the above and go ahead with interpretation of data.
I have huge data base collected from lab work and want to to process the data for these parameters with accuracy and confidence. Topics covered ranged from chemical adsorption, electrochemical methods of metal removal, COD removal, microbial and biotechnological methods for the same pollutants (almost).
Experts, please guide me in this regard, if any free software is available or even for purchase along with due instructions, etc.
I am wondering what will happen to the molecule if it's HOMO-LUMO gap will approach to zero.
Could the presence of ligand on a catalyst surface reduced the reactivity of its surface? If yes/no, please explain why?
we are working on metal sorption by biomass and our data is obeying both Langmuir and Freundlich isotherm in terms of R2 value between 0.8-0.9, then which adsorption constt is (Q0 or Kf )will better describe sorption capacity of biomass and what type of interaction it will follow
I have 2 experimental data,
1. varying concentration of heavy metal
2. varying dosage of adsorbent.
How can maximum adsorption capacity be calculated according to these experiments.
Or how can the maximum adsorption capacity be calculated by any procudure?
I want to know how to do interpretation from the graphs, please give reference if any & what is difference between them ?
1. Can anyone provide me the basic step by step protocol of Langmuir and Freundlich isotherm parameters for adsorption of pharmaceutically active compound (carbamazepine) from aquatic bodies using plant extract capped magnetic nanoparticle
2. how to calculate the Sorption and desorption experiment setup?
3. how to calculate the absorption kinectics?
I am trying to reduce a detailed mechanism, through various reducing methods such as DRG, DRGEP, Full species sensitivity analysis etc. What will be the final developed mechanism called? I mean whether it will be called skeletal mechanism or reduced mechanism? What is the difference between skeletal mechanism and reduced mechanism?
I am a mechanical engineer and have very little knowledge of chemical kinetics. Please suggest me some books or literature that can be helpful to understand the basics of chemical kinetics.
I have been using chemical kinetics equations (1st order, 2nd, order, etc) for modeling of adsorption /desorption of drugs on molecular sieves. Is this a correct or I need specific equations? I need good references . Can someone help me?
Both these phenomena are termed catalysis, but clear and complete discussion and specification of their similar and distinguishing features would be useful.
Is the topic 'prediction of hydrate conditions in gas pipeline' a chemical kinetics research work
I have seen people using 1.39 µm, 2,5 µm respectively. Currently, I am working with 1,392 µm to measure H2O. Also, one can choose the appropriate wavelength from the 'spectraplot' as well. Can anyone really suggest or have worked with a shock tube using TDLAS to study Chemical Kinetics?
Your valuable feedback in this regard would be really helpful. Looking forward to a response.
If I have a method for the measurement of kinetics parameters, how I can determine the different concentrations of substrate that I need use for obtain several initial velocities and generate the Lineweaver-Burk plot? and what kind of software is recomendded for the calculations?
i have done mtt assay many times..but unfortunately i couldnt acquire proper absorbency for my conditions even for my controls...the absorbency of my control isnt higher than 0.5---i dont know what should i do??
i have seed 15000 and also 25000 cells in each ninety six well plate but i couldnt get good result?
Does anyone have any idea about my problem?
I want to get the maximum concentration for carbon dioxide in an 0.5 M potassium bicarbonate solution
Has anyone please manage to write a code for the methane reduced mechanism mentioned in paczko's paper named "Reduced Reaction Mechanism for Meathne, Methanol and Propane Flames"? Because i don't know how to initialize the domain with zero concentrations of species H, H2O, CO, CO2, H2, M while they are needed in calcualting intermediate species.
I am doing H-abstraction reaction by OH radicals. I found one TS, Which is barrierless. Is it possible. What is reason behind it ?
I am doing a kinetic study on an enzymatic reaction which does not follow Michelis-Menten equations.
I am using a model to fit the experimental data, and it can fit the data for each given substrate concentration (mixed with different enzyme concentrations) very well, BUT the rate constant changes by changing the substrate concentration. In other words, the rate constant seem independent of the enzyme concentration, but somehow dependent on the substrate concentration. It should also be mentioned that in all conditions, the substrate is excessive.
I am wondering if this phenomenon is physically possible or something is wrong with the model.
It would be helpful if you could mention a reference that discusses the effect of different chemical kinetic mechanism to the emission predictions.
I'm looking for a good reduced or detailed chemical mechanism to simulate methane nitrous oxide premixed flames.
SanDiego mechanism (with nitrogen chemistry "add-on) and GriMech3 are both disappointing when it comes to predicting laminar flame speed.
The following article worked on an other mechanism named PPD, is this the most accurate mechanism nowadays ? Thanks
I am interested in knowing the equations for obtaining these properties and subsequently inserting them in a model.
Suggestions on texts, articles and web materials will be appreciated.
I want to calculate rate constants for CuO or Cu2O crystal growth formation. Please suggest an experimental or simulation technique to do that
I am working in the computational field of gas phase kinetics. Right now I am doing some unimolecular decomposition reactions. I want to calculate the rate constants of these reactions using RRKM Mesmer.
I am trying to find the best model to my data. The velocity (V) vs substrate [s] curve looks hyperbolic under normal conditions. When I introduce an inhibitor of interest at concentration of, say, 1 mM, the curve is low and flat. However, when the concentration of my inhibitor is at 0.5 mM, the curve is lower than the normal, but has a sigmoidal shape. This also occurs when the inhibitor under 1 mM is mixed in with one of its products of hydrolysis. Since the MM fit is not appropriate for all my curves I am looking at others, including the Hills equation because I believe the difference in shape has something to do with allosteric sites on my enzyme. I have a few questions:
1) I have been using the least squares method and Solver on Excel, with 'Vmax', 'Km' and 'n' as variable cells. These values are different for every curve, one results in n<1 and the rest n>1. Am I solving correctly?
2) Am I using the right model and how do I know?
3) It appears that Vmax decreases and Km increases with increasing concentration of inhibitor. I can't figure out what inhibition this is.
I'm trying to simulate pulsejet engine combustion using a matlab code, but i'm stuck at the combustion phase.
1) I should use "G. PACZKO, P.M. LEFDAL AND N. PETERS" mechanism mentioned in (REDUCED REACTION SCHEMES FOR METHANE, METHANOL AND PROPANE FLAMES), the problem here is i don't know how to implement a reduced chemical kinetic mechanism using the paper's definitions (global reaction rate and how to relate it to the molar concentrations of the species variation with time) ?
2) How do i implement that chemical mechanism in NS equations ? when to call it, what does it need as inputs, what will it give me as outputs, .. etc.
Any help would be so appreciated.
Or C 's reaction with B will be limited or lesser ?
I've seen the Modified Arrhenius equation in several forms. For instance, three kinds are attached.
Please consider the first attachment. There is an activation energy (Er). In some cases, authors do not use this form and they use the form just like two other form (see ar-2 and ar-3). They use "thetha" or "Tar". Now, I need to calculate Er from thetha/Tar. I think I have to multiply thetha or Tar by R. Am I right? R is universal gas constant and here its unit here is J/kgmol-K. I guess it should be 8314. Am I right?
Question: Calculate the equilibrium value of vacancies concentration for copper per atom of the order of 10^4 at 1000K the energy for vacancy formation is 0.9eV/atom.
Answer:N=N_0+exp(−Q/RT)is something that I know.However all that I could arrive is to calculate −Q/RT which calculates to give me 82.1.I have taken R to be equal to 0.0821 units and have taken T=1000K. Now I cannot proceed any further.I am not even sure what I am to calculate.
I calculated activation energies for intermediate stage of sintering for alumina+tetragonal zirconia composite and alumina+cubic zirconia composite via non-isothermal CHR method in microwave hybrid sintering, and compared them. The particle sizes of both as-received zirconia were same. A+tZ shows slightly higher activation energy as compared to A+cZ, but the densification of A+tZ is also higher. Can someone please guide? Because if densification is higher, then the activation energy for sintering should be lower, but that's not the case here. Is some unusual factor of sintering kinetics involved here?
I am dealing with the synthesis and characterization of PIR foams. In particular, I am monitoring the kinetics of these foams by FTIR (please find the spectra attached below). As well-known from the literature, the asymmetric CH stretching band at 2972 cm-1 (which remains constant during the reaction) is typically used as internal reference band to correct the density changes during the foaming process. In the same way, my question is if you know from the literature some reference band that may be used for PIR to the same purpose.
Please note that for PU a polyether polyol is used, while for PIR is used a polyester polyol.
Thanks in advance.
Does the dye degredation reaction with H2O2 over a heterogeneous catalyst can follow a zero order with respect to dye?
I am investigating how polyurethanes are affected by the degree of mixing. More in general, I am interested to study how the contact between the two reactants (in my case polyol and isocyanate), and as a consequence the reaction rate, can be affected by changing tre speed of the stirrer.
May you suggest me which parameter to investigate?
And, please, if you have some reference about this topic can you share it?
Thanks in advance.
What is the most cheapest procedure to soften the hard water, decontaminating it and reducing the high minerals contents
(Removal of magnesium and calcium ions in it)!
I have calculated thermodynamic data of different metal oxides and surface oxides through DFT calculation via material studio, does any body know any software or any other program to convert them into NASA polynomial format thermodynamic coefficient that can used for Chemkin modelling?
Thank you in advance
Atmospheric chemistry is very complex science with various processes work in tandem. Here, we discuss only about chemical transformations by ruling out transport and deposition processes, in the atmosphere. There are many chemical mechanisms available to choose from and work with for the chemistry and air quality studies. People work with either one mechanism for specific problem or many mechanisms as part of "intercomparison of mechanisms". A lot of such studies have been carried out so far.
Despite being it complex, one has to have kinetic level understanding of the processes in the modeling. Here, I would like to know if the atmospheric chemistry modelers have that understanding already. If so, how did they develop that skill?
I am a beginner of computational quantum chemistry, and I want to choose an effective software for the DFT calculation of thermodynamics and kinetics of chemical reactions.
I have noticed that there are many GPU-cuda accelerated computational quantum chemistry codes, such as, Gaussian, VASP, Q-CHEM, Quantum Espresso, CP2K, ADF, BigDFT, NWChem, TeraChem et al.
And would you please give me some advice on which code (with cuda) is faster and more suitable for me?
Thank you very much!
I've been trying to simulate this process with Aspen Plus and I transform the kinetic in POWERLAW term in aspen, but the water-gas shift reaction kinetic seem to be off, I find some references but any of them are the same. Can anyone help?
During chemical kinetic experiments, I have found a -1 (negative) partial order for one of the reactants. What does such a value physically mean, in terms of reaction mechanism?
Thanks by advance for your replies. If anyone could redirect me to a paper dealing with this topic, it would be nice.
So I am using Biacore T200 and want to perform a kinetics analysis on a small molecule that is bound to my protein of interest. My question is what parameters should I use, for example contact/dissemination time and flow rate. I have a problem as my results show two different curve sets, one at around 200s and another at around 900s. The 900s seems to be the correct one. What is going on?