The study of rates and steps (mechanisms) of chemical processes.

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Kinetics: Order of Reaction

I am confused as to how an order of a reactant (n or m) in the rate law can be negative. This means that increasing the concentration of a reactant would actually decrease its rate of disappearance. ...
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Related to chemical kinetic [duplicate]

I have no idea about this question's title, so please correct me. I have general knowledge on rate reaction, but these questions are still puzzled me. First, consider this question as an example: ...
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Conc. vs Time Graph for Second Order Reaction

From my understanding plotting the conc. over time for a 0-order reaction yield a negative linear slope. Plotting conc vs time for a first order reaction intuitively yields an exponential type slope. ...
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Finding molarities of individual reagents given the chemical equation and total concentration in a container

I am given a table that gives me the different total pressures at certain times. The decomposition of phosphine is the reaction: $$\ce{4 PH3(g) <=> P4(g) + 6 H2(g)}$$ The time/pressure ...
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Find the molar concentration of O₂ and SO₃, when the molar concentration of SO₂ is 0,01 [closed]

We have the reaction: $$\ce{2 SO2 + O2 -> 2 SO3}$$ The initial concentration of the reactant is 0,02(I created this value as our teacher forgot to mention. Find the molar concentration of ...
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How to Determine the Rate Law knowing time and concentrations

Consider the hypothetical reaction described by the following equation: $$\ce{3 A + 2 B -> C}$$ Reagent B was added in excess and the following time concentration data was obtained. ...
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How to calculate the rate constant at a certain temperature, given first order rate constants at different temperatures? [closed]

I have this problem that I am trying to study for my test: A reaction has first order rate constants of $4.82 \cdot 10^{-5}~\mathrm{s^{-1}}$ at $25~^\circ\mathrm{C}$ and $1.41 \cdot ...
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kinetic and thermodynamic parameters of biodiesel production from lard

I want to know if someone has experimental results and calculations of the kinetic and thermodynamic parameters of Base Catalyzed Transesterification of pig fat, if not which is the method used to ...
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Pseudo 1st order Kinetic reaction

The pseudo 1st order reaction happens when one of the reactant is in large excess and its concentration doesnt change during the reaction . Is there any other such situation when a certain higher ...
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How is the rate of a reaction defined?

I have learnt for many years that rate of reaction is the rate of change of concentration of a reactant or product with respect to time. I never questioned this before, but recently I have been ...
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Kinetics vs Thermodynamics

The way kinetics is taught at the undergraduate level (Arrhenius and collision theory) chemical equilibrium is determined governed immensely by activation energy of the reaction. According to ...
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Is it possible to derive integrated rate law algebraically?

Here is the calculus way: I have no prior knowledge of calculus. But my teacher asks me to derive the integrated rate law for any order between one to ten. It would be fine for me to memorize the ...
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How does an ice bath change the rate of an reaction?

If I had hydrogen peroxide decompose with the help of manganese dioxide and measured the time taken for the reaction to complete and the volume of oxygen collected. I will get a graph that looks like ...
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Oxide surfaces develop a charge in H2O. Do we have any, even vague, handle on how long does an indivdual charge last on avg. before being neutralised?

We often know, from e.g. titration experiments, what the average surface charge density of a surface is. How do these charges vary over both time and space (i.e. dynamics)? I have been unable to find ...
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Reaction Kinetics and Stoichiometry — Mass conservation

This question has been bothering me for some time, and I can't seem to find a good answer online. Say I have four chemical species $\ce{A}$, $\ce{B}$, $\ce{C}$, $\ce{D}$, and these four react in the ...
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Predicting rate equations from data

I am having trouble wit the following question on my problem sheet: "The reaction $\ce{Br- + ClO^- \to BrO^- + Cl^-}$ occurs with a rate constant of $\text{0.35 dm}^3 \text{mol}^{-1} \text{s}^{-1}$ ...
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Second order reaction half life equation?

For the reaction: $$2A\to p$$ The rate, $v$ may be given as: $$v=-\frac12\frac{d[A]}{dt}=k[A]^2$$ Correct? Integrating this gives: $$-\frac12\int_{[A]_0}^{[A]}\frac{d[A]}{[A]^2}=k\int_0^tdt$$ ...
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Calculating the rate of hydrolysis experimental

I am going to do a laboratory practical where we hydrolise halogenoalkane and determine the rate of reaction, this by adding silvernitrate that reacts with the formed halogenide and precipitates. My ...
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How to make sense of the 'Relaxation Method' for measuring reaction kinetics?

I get the concept that one can measure the rate of reaction by measuring the rate at which an equilibrium state reaches another equilibrium state after the system is perturbed (usually by heating). ...
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Is there a name for the intersection of the graphs of first and second order reactions?

Is there a name for the point where a first order rate of reaction meets a second order one. This point highlighted above.
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How is the Rate Law of a reaction measured?

What is Rate Law of the reaction below?$$\ce{4 HBr + O2 -> 2 H2O + 2 Br2}$$ How do we approach finding the rate law of reaction? Can this be found out only through experiments?
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Why is the rate of disappearance negative?

Rate of disappearance is given as $-\frac{\Delta [A]}{\Delta t}$ where A is a reactant. However, using this formula, the rate of disappearance cannot be negative. $\Delta [A]$ will be negative, as ...
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Why is it not possible to determine the rate constant this way?

The following equation can be used to determine the rate: $Rate = \frac{-\Delta [A]}{\Delta t}$ This equation can also be used: $Rate = k[A]$ By simple substitution, $\frac{-\Delta [A]}{\Delta t} = ...
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In the elementary steps of a reaction, why do we assume that the coefficients of a reactant corresponds to its order?

Recently, I was taught that the coefficients of the reactants in an elementary step of a reaction indicates that reactant's order. Why is this the case? I thought that the order of a reactant was not ...
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Why is the units of kcat 1/s?

I understand that $k_\text{cat}$ measures the turnover number of an enzyme. This measure is therefore a quantity of molecule conversions per unit of time. I suspect that my problem is more that of a ...
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What are the possible concentration pathways for a 3-species system?

Inspired by this question, which asks if a multi-species system could oscillate around its equilibrium, I thought about the possible concentration pathways the following more narrow specified system ...
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How to solve an Arrhenius equation problem?

A widely used rule-of-thumb for the temperature dependence of a reaction rate is that a ten degree rise in the temperature approximately doubles the rate. This is not generally true, especially when a ...
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Does product induced poisoning qualify as a rate limiting step?

I have a question about whether a particular situation qualifies as a rate limiting step. I have a catalyst that under normal conditions gets poisoned when products accumulate on the catalyst surface. ...
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Stuck with derivation of the integrated rate equation for a pseudo first order equilibrium reaction

I was reading about the integrated rate law. However I have problems to follow the solution. I have an equilibrium reaction: [A]+[B]=[AB] with forward and back reaction. I approximate the ...
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Can there be more than one combination of reactant/product concentration for a specific equilibrium constant?

For an elementary reaction like $$\ce{A + B -> AB},$$ $$K_{c} = \frac{\ce{[AB]}}{\ce{[A][B]}}$$ and $$\frac{\mathrm{d}\ce{[AB]}}{\mathrm{d}t} = k\ce{[A][B]}.$$ If I let the reaction reach ...
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Why does radioactive decay occur?

Is there a reason radioactive decay is exponential, as in after an extremely long time some of the original compound remains, or is this just an empirical model? Also, why does $\ce{^{238}U}$ have a ...
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Iodine and persulfate kinetics: What can be deduced from graph?

From a graph of iodine concentration vs time of the reaction of iodide with persulfate, what can be deduced? Is it possible to find the order with respect to iodide and with respect to persulfate?
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Finding rate constant at different temperature

For the reaction $$ \ce{2N2O5(g) -> 4NO2 + O2(g)} $$ the rate law is: $$ \frac{\mathrm{d}[\ce{O2}]}{\mathrm{d}t} = k[\ce{N2O5}] $$ At 300 K, the half-life is 2.50·104 seconds and the activation ...
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What is the non-ideal equivalent of mass action kinetics?

Starting from the equations of mass action kinetics, one may show that (for suitably chosen numbers $A_i$), the function $\sum_i x_i(A_i + \log x_i)$ is a Lyapunov function, i.e. it decreases over ...
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Improving a mathematical model of a chemical reaction

I want to improve a mathematical model to suggest a rate expression. How can I do it by using relative absorbance values? The reaction is UV-catalyst decomposition. I don't know concentration values ...
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“There are no chemical cliffs”

Are there any reactions with no activation energies? Prof just told us there are no chemical cliffs. Is this true? I read something about nuclear decay as being a reaction with no activation ...
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Finding Root-Mean-Square of Ne using kinetic energy?

I am not being able to solve the following question: -Find the root-mean-square speed of $\ce{Ne}$ atoms at the temperature at which their kinetic energy is $\mathrm{6.24\ kJ/mol}$. I tried ...
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How can a catalyst not be included in a rate equation, if it by definition speeds up a chemical reaction?

I thought that anything not in a rate equation was automatically zeroth order and therefore did not affect the reaction? But I have heard that catalysts can be involved in a reaction while not being ...
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Radioactivity and Kinetics of disintegration

Well I've just started on kinetics and there are a few things I am absolutely confused about! First of all , is neutron actually made up of a proton and electron? if yes then how is it possible? In ...
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A few basic questions about activation energy and the Maxwell-Boltzmann distribution

I understand activation energy to be the relative difference in energy between that of the activated complex/transition state (at some temperature) and the average energy of the reactants like shown ...
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Oxidation of formate ion by peroxydisulfate in water solution: Why are there “strange” kinetics?

As you can see, the first step is the slowest, but by using the rate-determining step approximation you wouldn't arrive at the correct rate law which is: $r=k\ce{[HCOO^{−}]}^{1/2} ...
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Rate law and rate constant [closed]

How do we obtain the expressions for integrated rate laws ?!? What are the limits we integrate it under and with respect to what do we integrate it?
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Reversible elementary reaction

I have a question regarding a reversible elementary reaction: If we have an equilibrium where $$\ce{A<=>[k_1][k_{-1}]B}$$ , then $$-d[A]/dt= k_1[A]-k_{-1}[B]$$. If we take $$[B]=[B]_0 + ([A]_0 ...
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Significance of Kinetic Velocities?

In the concept of Kinetic Molecular Theory we have rms(root mean square), avg(average) and mp(most probable) velocities. I understand the concept well. But my question is why do we have three ...
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Molecularity vs Order Of Reaction

In the field of Chemical Kinetics, terms like Molecularity and Order Of Reactions are often used. I am a bit confused between these two terms. Can someone explain to me about these two terms and ...
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What is the constant of integration in a series reaction in chemical kinetics?

I have a question regarding the rates for a series reaction in kinetics. So imagine $\ce{A -> B -> C}$, with $k_1$ as rate constant for $\ce{A -> B}$ and $k_2$ as rate constant for $\ce{B ...
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Why is proton transfer so fast?

Why is proton transfer always kinetically favored? In other words, why are Bronsted acid-base reactions so quick? Is it because protons are generally unhindered, sterically? This seems plausible; ...
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Formation of 2,4-Dichlorophenol by free chlorine mediated oxidation of Triclosan

I cannot find much guidance in the literature. This is the reaction between free chlorine in water and triclosan. I understand ether cleavage and electrophilic aromatic substitution (maybe) involved. ...
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Rates of reaction

Assume a reaction is of second order kinetics and that the rate constant is k. The differential rate equation is given by: A+B->Products -dCa/dt = kCaCb Show that the general expression of ...
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Can in any case the faster step of the reaction be rate determining?

I found a sentence in book which states the reverse step of this reaction ( I forgot what was it!) has the faster step as rate determining . Even Rate determining step-Wikipedia states: In ...