Questions tagged [kinetics]

The study of rates and steps in mechanisms of chemical processes.

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Maintaining our supersaturated oceans

Supersaturates solutions can be unstable and decay beautifully once a seed crystal is introduced. Our oceans near the surface are supersaturated with respect to calcium carbonate. This map shows the ...
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Where can I get thermodynamic and kinetic constants of Michaelis-Menten?

I need the three rate constants values ($k_1,k_{-1}$ and $k_2$) for any Michaelis-Menten like enzymatic reaction, not only the $K_M$ usually reported. Besides the $\Delta G$ of the two reactions ...
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Surface-water hydrolysis reaction & reaction/adsorption kinetics model

I didn't major in Chem or Chem Eng when I was an undergraduate, so I have a rather limited background in this field, please forgive me if my questions are too basic or very wrong. I wish to model a ...
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Does pressure affect rate constant? [duplicate]

I would like to know if pressure affects rate constant. Suppose pressure affects the rate constant. Does it depend on partial pressure (like: if I add an inert gas to the system), or only increasing ...
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1answer
63 views

TCP and KCP product

Q: According to me, the kinetic controlled product(KCP) should be While the Temperature controlled product(TCP) is: What should be the answer to this question because no temperature has been ...
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1answer
68 views

How does the rate equation account for solids and liquids?

The question is long because I wanted to include the whole thought process. Given the hypothetical reaction: $$\ce{ A(s) + B(aq) <=> C(aq) + D(aq)}$$ One would obtain the equilibrium constant: $$...
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Rate of Decomposition of Sodium Thiosulphate

I want to calculate the activation energy of the decomposition of sodium thiosulphate, as a part of my school research project. I am aware that I must use the Arrhenius equation where the rate of ...
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1answer
55 views

How does the boiling point of water inside a pressure cooker change with temperature? [closed]

My question is why a pressure cooker would affect the boiling point at all. To my understanding, the boiling point of a substance is defined by 'The temperature at which the vapor pressure of the ...
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1answer
33 views

why is $f_{ES}=\frac{[S]}{[S]+K_M}$

I'm working my way through the chapter on enzymes in "Biochemistry" with Stryer et. al, 9th edition. In the current paragraph it's claimed that the fraction of active sites bound to ...
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98 views

Can an elementary reaction have zero order?

I am very confused right now about my approach to this question could somebody help me out with this. I reasoned my answer as given below Let's assume if a complex reaction is of zero order. It ...
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Time between hoops appearing in a non-stirred BZ reaction

From what I know, if you start a Belousov-Zhabotinsky reaction in a petri dish, instead of the mixture changing color, hoops would appear periodically. But I can't seem to find anywhere, is there a ...
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For an a plot of lnk against 1/T from Arrhenius equation, why does the y-intercept change when Ea changes?

According to Arrhenius equation, k = Ae^(-Ea/RT). Thus graph of lnk against 1/T is a straight line with negative gradient and positive y intercept. To plot a graph for lower activation energy, the ...
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117 views

Comparing Rate of Hydrolysis of Acyl halides

In this particular question, my answer is (D) as steric hinderance is minimum there, but answer (B) was given due to the electron withdrawing (-M) effect of the nitro group. Isn't steric hinderance ...
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Ease of reaction of hydrogen with alkali and alkaline earth metals

The ease of reaction of group 1 metals with hydrogen decreases as we go down the group. But why lithium requires high temperature than sodium, potassium and rubidium? What is exactly "ease of ...
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Number of gas molecules in activated state vs normal state

I have a simple bimolecular reaction $$\ce{A + M <=>[k_2][k_1] A^* + M}\tag{1}$$ where $\ce{A}$ is a molecule which collides with another molecule $\ce{M}$. $\ce{A^*}$ is the $\ce{A}$ molecule ...
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Why we are dividing rate of reaction with respect to a species by its stoichiometry coefficient to find rate of that particular reaction

If there is a reaction like this $$\ce{ H2 + Cl2 -> 2HCl}$$ I can understand that each individual species (reactant or product) can have different rates and we can compare them like this, $$-\frac{...
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Can an alloy catalyst change during a reaction?

I am studying the reaction pathway of oxygen evolution reaction (OER) on a PtNi alloy catalyst using density functional theory (DFT). What I found is that, for different intermediates, the most stable ...
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Do decomposition potentials change during electrolysis?

I was just wondering if decomposition potentials actually change during electrolysis. For example, if we reversed the Daniell cell reaction so that copper is oxidized, the half cell reactions would be:...
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Deriving kinetic equations for reversible reactions

Problem Given the reaction $\ce{A <=>[$k_\mathrm f$][$k_\mathrm b$] B}$ with rate constants $k_\mathrm f = \pu{4E-2 s-1}$ and $k_\mathrm b = \pu{10^{-2} s-1}$. Initially, $\pu{2 mol}$ of $\ce{A}...
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Are catalyst concentrations included in the rate expression?

I have seen different rate expressions, some which include the concentration of the catalyst as a term in the rate expression, and others that do not. I thought the rate expression only includes terms ...
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Is there a easy way to estimate how quickly something will dissolve depending on its surface area?

How exactly does the surface area of a solid for example a cube of sugar, affect the speed of its solvation. I guess everyone has observed that a batch of fine grounded sugar or salt dissolves much ...
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1answer
123 views

What is an intuitive explanation for the exponential form in the Arrhenius equation?

What is an intuitive explanation for the exponential form $\exp(-\Delta E/(kT))$ in the Arrhenius equation? While I know the reaction rate theory, I am puzzled by the origins of the form of the ...
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How practically to determine dispersion's Hamaker constant using CCC?

I know that Hamaker constants can be determined from CCC data. $$ccc=\frac{9.85 \cdot 10^4 \epsilon^3 k_B^5 T^5 \gamma^4}{N_A e^6 A^2 Z^6}$$ Where, $\epsilon$ is solvent dielectric constant, $N_A$ is ...
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Are pseudo-zeroth order reactions possible?

Are pseudo zeroth-order reactions possible? I have been taught that pseudo first-order reactions take place and they can be considered pseudo zeroth-order reactions because one reactant is in excess ...
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1answer
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How is the equilibrium expression (law of mass action) related to the rate law? [duplicate]

Every chemistry textbook I've read will have a chapter on the rate law. It will say something like, given a reaction $a\text{A} + b\text{B} \rightarrow c\text{C} + d\text{D}$, the rate law (for the ...
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1answer
46 views

Is there any relation between reaction quotient and rate constant in the context of order of the reaction?

How many times will the rate of the reaction $$\ce{2 A + B -> A2B}$$ change if the concentration of substance $\ce{A}$ is doubled and that of substance $\ce{B}$ is halved? The given solution takes ...
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Why is the concentration of gases denoted in form of partial pressure? [duplicate]

In most of the chemical laws of chemistry involving concentration of products or reactants like equilibrium constant, reaction quotient, Henry's law, Nernst equation etc, I often see a similar note ...
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1answer
126 views

Can't fit an exponential curve to the decomposition of hydrogen peroxide

I have carried out an experiment on the $\ce{MnO2}$ catalyzed decomposition of hydrogen peroxide. I would have expected the reduction in concentration to be exponential but when I fit an exponential ...
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1answer
79 views

How do the terms in a rate law relate to effectiveness and number of collisions of reactants?

In chemical kinetics, we use rate law to find the instantaneous rate of reaction. Let us consider a simple reaction $$\ce{aA + bB -> products}$$ where the rate law is $$\mathrm{rate} = k[\ce{A}]^a[\...
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1answer
71 views

What happens in a unimolecular reaction? [closed]

Molecularity is defined as the number of molecules required to collide simultaneously to form a product in an elementary reaction. In a unimolecular elementary reaction, do two molecules of the same ...
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2answers
685 views

How to estimate the temperature needed to overcome an activation energy barrier?

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 ...
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1answer
44 views

Why is oil solubility improved in solvents at higher temperatures?

This is in the case of extracting plant oil using a solvent extraction method for the purposes of biodiesel production. In a paper, it is stated that increased oil yield may be due to the 'increase in ...
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What is the rate constant k for the reaction between potassium manganate and oxalic acid?

For my school's chemistry classes, I am investigating the kinetics of the redox reaction between $\ce{K2MnO4}$ and $\ce{C2H2O4}$. I analyzed the data using a colorimeter set to $\pu{565nm}$. ...
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1answer
52 views

Finding the rate of a reaction given experimental data for reaction kinetics [closed]

Here is the question: For the reaction: $$\ce{2 A + 2 B → C + D}$$ The following data was obtained from three experiments: \begin{array}{c|ccc}\hline \bf{Experiment} &\textbf{[A] (mol/L)} &\...
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Confused about what to put as the x, y in the picture regarding chemical kinetics

I don’t understand what I should put as the x, y...I drew...is it a stechiometric coefficient or an order number? The pictures seem conflicting to me. Am I getting something wrong?
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3answers
261 views

Rate of a reaction when volume of the system varies with time

Background I was solving this question from this book and I was not able to get any of the options. The gaseous reaction $\ce{n_1 A_{(g)} -> n_2 B_{(g)}}$ is first order with respect to ‘A’. The ...
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Explanation of the trans-effect (thermodynamic and kinetic) for octahedral transition metal complexes

The thermodynamic trans effect refers to the ground state weakening of the metal-ligand bond in a complex by a ligand trans to it. The kinetic trans effect is the lablisation of a ligand in a complex ...
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How to graph a second order reaction with two different reactants

In a laser flash photolysis experiment, $\ce{C6H5NH2}$ $(C_0 = \pu{60 \mu M})$ is oxidized to the corresponding radical cation. The disappearance of radical cation is monitored spectrophotometrically ...
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1answer
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Energy per atom in a parallel radioactivity equation [closed]

I was reading an example in my textbook and the question goes like this: In a parallel radioactive decay, find energy liberated per atom of 'A' in MeV. The solution is proceeded like this: $$ \...
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Steady-state approach - how to find rate equation for intermediate?

The reaction mechanism for the formation of $\ce{NO2}$ is: \begin{align} \ce{NO + NO &<=>[$k_1$][$k_1'$] N2O2} & &\text{ (slow)} \\[0.2cm] \ce{N2O2 + O2 &->[$k_2$] NO2 +NO2} &...
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Steady state approximation for three-step cycle

How to write the steady state for $\ce{A}?$ $$\ce{A ->[$k_1$] B ->[$k_2$] C ->[$k_3$] A}$$ Species $\ce{A}$ seems to appear on both side of equation as it uses itself to produce some of ...
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Can anyone explain, why there are coefficients 2 in the equation for rate of change [A]?

The reaction mechanism for the decomposition of $\ce{A2}$ is thought to be: \begin{align} \ce{A2 &<=>[$k_1$][$k_1'$] A + A} & &\text{ (fast)} \\[0.2cm] \ce{A + B &<=>[$k_2$]...
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How to calculate the quantum yield of a photochemical process?

I have that $\pu{100 ml}$ of an aqueous solution containing $\pu{1.0 mM}$ $\ce{H2O2}$, $\pu{100 mM}$ $\ce{CH3OH}$ and $\pu{200 mM}$ DMSO are exposed to monochromatic light with a wavelength of $300$ ...
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Correct Rate Equation for a Reversible Reaction

I'm helping my son with Matlab as he is having trouble learning differential equations as they apply to chemical kinetics. His task is to solve for the equilibrium concentrations for a reaction $$\...
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Temperature at which the reaction Oxalic acid + KMnO4 becomes autocatalytic

As described many times, the reaction between oxalic acid and potassium permanganate can be autocatalytic due to the production of Manganese ions. I've read that this only occurs at higher ...
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1answer
276 views

Does mass affect rate of reaction?

Suppose I am reacting HCl with CuCO3. Experiment 1: I use 2g powdered CuCO3 Experiment 2: I use 4g powdered CuCO3 All other variables are kept constant. Will this have any affect on rate of reaction? ...
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Determine vmax and enzyme concentration (Michaelis–Menten)

I am given that the enzyme concentration is $\pu{15 nM}$ and the following data: $$ \begin{array}{rl} \hline S/\pu{mM} & V/\pu{mM s^{-1}} \\ \hline 1 & 0.202 \\ 2 & 0.368 \\ 5 & 0....
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Radical Chain Reaction, termination steps

In the termination step of radical chain reaction, we often neglect the recombination of hydrogen atom radicals and it will not be included in the mechanism. Let say the reaction is between $\ce{H2}$ ...
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1answer
223 views

Which alkene reacts faster with HCl?

Which alkene reacts faster with HCl? The logic tells me the most stable alkene 2 which is the most substituted would react the slowest. On the other hand, it would form the most stable tertiary ...
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1answer
170 views

The effect of dilution on the rate of a system in equilibrium

I'm attempting to answer a question from my textbook, however the answer that the textbook provides doesn't make sense to me. The question: Laura, a VCE chemistry student, loves graphs and wanted to ...

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