Questions tagged [kinetics]

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

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Why doesn't molecularity ever exceed 3?

Recently, I learnt that molecularity of a reaction is limited to 3 and even that is quite rare. I searched online and asked my teacher about this but the explanation given was that it is difficult for ...
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In a second order reaction, how can we have different slopes on constant temperature

I have the graph bellow, which is related to the reaction between H2O2 and Pyruvate. Each of the reactants are first order, so the overall reaction is second order. In that case, the relative equation ...
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Does manganese reacts with water at "not" standard conditions?

In my answer, I stated that manganese is said to not react with water under normal conditions although some sources say it reacts with water to liberate hydrogen gas. Does it implies that it reacts ...
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Are there any well documented reactions with "persistent" intermediates

I'm a biology and/or math person, not a chemistry person. I have only taken the standard sequence of undergraduate courses up to organic chemistry, and that was some time ago, so please excuse (and ...
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Confusion regarding order of reaction

The following points are given in my textbook about order and molecularity:- (i) Order of a reaction is an experimental quantity. It can be zero and even a fraction but molecularity cannot be zero or ...
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Reaction kinetics data for ethylene dimerization to produce but-1-ene

I am trying to simulate ethylene dimerization reactor (CSTR) in which Ethylene (in gas form) will be feed to a liquid phase reactor (operating at 50-53 deg. C temperature and 23 bar (g) via sparger ...
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What are the reaction rate constants, or coefficients, of coal combustion at high temperature?

Say I have coal that I will combust with $\ce{O2}$ at a high temperature of $\pu{1600-1800 K}$, what are the reaction rate constants, or coefficients, of the main reactions? I have searched around ...
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In a multi-step reversible reaction, is the rate-determining step the same for the forward and reverse reaction?

Consider the following reversible, multi-step reaction: For the forward reaction, the rate-determining step is the first step, because it is the slowest. Is the reverse reaction's rate-determining ...
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Can a spontaneous reaction have zero or negative activation energy?

Is it possible for a certain spontaneous reaction to have zero or negative activation energy? My high school teacher explains that it shouldn't be possible since it breaks the Arrhenius equation, ...
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Why is effervescence endothermic?

The reaction of sodium bicarbonate and sulfuric acid is quite endothermic... it seems. Of course, the chemical change is actually exothermic, but from what I've read, the production of carbon dioxide ...
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Calculate the concentration of the reactant from the absorbance of the product without molar absorptivity

Given the reaction $\ce{A->B}$, where the absorbance of the product $\ce{B}$ has been measured (see the table below), and the initial concentration of $\ce{A}$ is $\pu{10^{-4} M},$ calculate the ...
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Rate of polymerization for copolymers with two monomers

I've found in textbooks that for a chain growth homopolymerization the rate of polymerization $r_\mathrm{p}$ is $$r_\mathrm{p} = k_\mathrm{p}\sqrt{\frac{f_\mathrm{kd}}{k_\mathrm{t}}}c_\ce{A}^ac_\ce{B}^...
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Tmax of parallel reactions/Steady state reactions

Below are four reactions, to this experiment inhibitor is added so that k$_3$ = $0$ (but the other reactions are unaffected) calculate [D] when the reaction is over. The initial concentration of A is $...
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Deviation from (pseudo-) first-order kinetics during hydrolysis of sucrose

In an experiment we conducted at university, we studied the reaction kinetics of the acid catalyzed (with HCl) hydrolysis of sucrose to glucose and fructose (via the measurement of the polarization ...
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Why is it that first order reactions never end? [duplicate]

I'm studying chemical kinetics in high school. We are studying Integrated Rate Equation of first order reactions - their derivations and graphs. Our teacher showed us a graph of: Concentration of ...
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How to calculate rate of carbon dioxide from rate equation? [closed]

The concentration of carbon dioxide that changes with time: $$\ce{CO2(g) + H2O(l) <=>[$k_\mathrm{fwd}$][$k_\mathrm{rev}$] HCO3-(aq) + H+(aq)}$$ How to calculate the integral for the following ...
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Determine reaction order of Cyclopentadiene

Reaction: $\ce{2 C5H6 -> C10H12}$ For this reaction it is stated that $\pu{0.609 M}$ cyclopentadiene was formed in an ethanol solution. When the solution was heated $(\pu{40 ^\circ C})$ and ...
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Example of reactions series A → B followed by A + B → 2 C

I'm currently writing about geometric numerical integration and I need an example of the following series of chemical reactions: \begin{align} \ce{A &->[$k_1$] B} \tag{R1} \\ \ce{A + B &...
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3 votes
1 answer
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Work done by gases on each other in the process of mixing them

I was wondering if gases, which are in the process of mixing, do any work on each other. I haven’t found many resources on this. We all know that gases, which have a higher pressure than their ...
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How can the reaction heat be ignored in an energy balance?

I have received from my professor the following (here summarized) problem: A first-order exothermic reaction A->B takes place in a tubular reactor (typical PFR). The tube is cooled to a constant ...
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Definition of Molecularity of a reaction? [closed]

If nucleophilic attack occurs simultaneously at two seperate electrophilic sites of the molecule following SN2 at each site, will the moleculularity still be 2? Does molecularity depend on the total ...
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1 answer
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Combining two reactions in equilibrium with same reactants but different products: What would be the new K?

If I have the reactions : A(g) ⇌ B(g)   K1 A(g) ⇌ C(g)   K2 Am I able to add the equations like done in Hess's law despite nothing canceling out? And if I can do so, is the new equilibrium ...
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How to dissolve metallic lead fast in nitric acid?

We were trying to dissolve a piece of metallic lead in concentrated nitric acid until we found out that concentrated nitric acid is not a suitable media, as long as it produces a layer of lead oxide ...
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Reaction rate of 2 H2 + O2 → 2 H2O

I am interested in the kinetics of the reactions: $$ \begin{align} \ce{2 H2 + O2 &-> H2O}\tag{R1}\\ \ce{2 CO + O2 &-> 2 CO2}\tag{R2}\\ \end{align} $$ I looked at the NIST website hoping ...
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2 votes
1 answer
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Relation between concentration and activation energy

Will increasing the concentration of the reactants in a chemical reaction increase the proportion of molecules with an energy greater than the activation energy $E_\mathrm{a}$? It seems to me that the ...
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Rate equation for the decomposition of hydrogen peroxide with iron(III) chloride as catalyst [duplicate]

I am trying to determine the activation energy of the decomposition of hydrogen peroxide with iron(III) chloride added as a catalyst. To do that, I need to find the rate constant, but I am not sure ...
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Ligand-receptor kinetics with two ligands - is this a correct formula?

I'm not a chemist nor a pharmacologist but a psychiatrist, so forgive me for my shallow understanding of the topic. My interest is primarily educational and for my own benefit in order to gain deeper ...
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Parabolic Arrhenius plot

I am currently doing a kinetic study on an enzyme catalysed reaction and plotting the Arrhenius graph ($\ln k$ vs $1/T$) and I got a parabola. My idea is to take the derivative at each point, meaning ...
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Can you use Michaelis–Menten kinetics to model the ATP production rate for glycolysis and OXPHOS with glucose as a substrate?

I am an applied mathematician researching cell metabolism, but I have little experience in biochemistry. Currently, my PI and I are considering using Michaelis–Menten kinetics to study how varying ...
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How to apply the Geiger–Nuttall rule to find half-life?

I'm having trouble understanding the Geiger–Nuttall rule for α-particle decay. From the textbook I'm using, the rule is defined as $$ \log(t_{1/2}) = A + \frac{B}{\sqrt{Q_\alpha}}, $$ where the ...
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Are good leaving groups good in both directions?

In biology, phosphate groups are often used, good leaving groups. If I had an opposite case, where a phosphate group remains bound to an enzyme while the main substrate is removed (e.g. E-P04-S => ...
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Will the rate of the reaction of discoloration of crystal violet change if I vary the concentration of crystal violet?

I'm trying to find a relationship between the concentration of crystal violet (limiting reagent) and the rate of reaction in the hydroxide medium. I've only seen examples of experiments varying the ...
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1 vote
1 answer
150 views

Finding the reaction order from a given plot of chemical kinetics

What will be the order of the reaction for a chemical change having $\log t_{1/2}$ VS $\log a$ Where $a=$ Initial concentration of reactant and $t_{1/2} =$ Half Life? 0 order 1st order 2nd order None ...
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Rate of Reaction - Potassium Permanganate and Hydrogen Peroxide

I'm interested in an aerospace project that requires I know the reaction rate ($[\pu{M/s}]$) of, $$\ce{2 KMnO4 (aq) + 3 H2O2 (aq) -> 3 O2 (g) + 2 MnO2 (s) + 2 KOH (aq) + 2H2O (l)}.$$ I'm just ...
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2 votes
1 answer
136 views

Why does cyclopentadiene react faster than cyclohexadiene in Diels Alder reactions?

How does the length of the bridge of the resulting bicycle change the rate of the Diels Alder reaction (examples below)? I can't seem to think of how one would be more electron donating than the other ...
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2 votes
3 answers
633 views

Why does increasing electrolyte concentration increase the rate of electrolysis?

I'm a Chemistry teacher and have students who are performing an experiment to determine the effect of copper ion concentration on the rate of solid copper formation at the cathode in an electrolytic ...
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When should the Steady State Approximation be used?

In class, I learned that we should use the steady state approximation when there are multiple slow steps or if the rate determining step is not known (shown on this Chem Libre link). However, further ...
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Which theory could describe rate constant for photodissociation?

I am considering photodissociation reactions and want to find an appropriate theory to describe how one could determine the rate constant. I know Rice-Ramsperger-Kassel-Marcus (RRKM) theory is for ...
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1 answer
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Writing rate of disappearance and rate of appearance using rate law [closed]

I have studied that rate of disappearance and rate of appearance is the change in concentration of reactants and products (respectively) with respect to time. Thus, $$\text{ROD} = -\frac{\Delta c_R}{\...
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Assuming 2O3 (g) → 3O2 (g), how much oxygen will be formed within 5.50 s for a reaction rate of 0.250 M/s?

Context: The rate of appearance of $\ce{O2}$ in the reaction: $\ce{2O3 (g) -> 3O2 (g)}$ is $\pu{0.250 M/s}$. So, over the first $\pu{5.50 s}$, will it form $\pu{1.38 M}$, or $\pu{4.13 M}$ of oxygen ...
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-1 votes
2 answers
564 views

What is the rate law of a reaction: 2A + 3B → products? [closed]

Update: I found out that the coefficients of the chemical reaction are not the exponents in the rate law. It is actually the order of the species during the reaction. It is known that in the reaction, ...
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5 votes
2 answers
200 views

Dissolution of sugar in water and its temperature dependence

As far as I can remember, I was taught in 6th grade that warm water would dissolve sugar with greater ease than cool water. In 11th grade, I was taught that Hydrogen Bonding is the reason behind ...
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3 votes
0 answers
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How long would atmospheric oxygen last on Earth if plants stopped making it? [closed]

A few years ago a rather dubious paper appeared in a mathematical biology journal. The gist of it was that warming oceans could stop oceanic plankton making oxygen (according to a somewhat simplistic ...
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1 vote
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Bond frequency vs Bond Strength in Kinetic Isotope Effect

I am confused by the following: in Ansyln's Modern Physical Organic Chemistry, a higher vibrational frequency defines a stronger bond due to the deeper/sharper potential well (page 76). However, the ...
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2 votes
2 answers
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Reaction kinetics of exothermic reaction

A colleague said we can’t dissolve a salt (whose solvation enthalpy is exothermic) faster if we increase the temperature (the solubility equilibrium product is not reached) because Le Chatelier‘s ...
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1 vote
1 answer
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Is the rate-determining step equal to or the lower limit of the overall reaction rate?

I’ve heard many conflicting points on this single question alone. Even the usually reliable sources I run to are pretty ambiguous on the matter. So now I’m here, after 1 and a half weeks of confusion. ...
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1 answer
102 views

How to relate equilibrium constant and equilibrium conversion?

For the following gas phase reaction: $$ A\leftrightarrow B $$ The concentration equilibrium constant ($K_c$) can be expressed as: $$ K_c = \frac{c_B}{c_A} = \frac{\frac{F_B}{\vartheta}}{\frac{F_A}{\...
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Briggs-Rauscher reaction doesn't oscillate and turns blue with Vitamin C

I tried to recreate the Briggs-Rauscher reaction by using a solution of $\ce{H2O2}$, $\ce{KIO3}$, $\ce{H2SO4}$, $\ce{CH2(COOH)2}$, $\ce{MnSO4}$ and a soluble starch. I used this recipe. In container ...
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Bromine Clock reaction

Why doesn't the bromine react with the methyl red at the start of the bromine clock reaction? I assume the rate of reaction (and rapid removal) of bromine with phenol is much, much, much faster than ...
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11 votes
2 answers
729 views

True or false: "If a reaction has a large negative value of ∆G, then it will be a fast reaction."

I recently took a Gen. Chem. 2 exam that contained this question. I answered false, as I knew that thermodynamics and kinetics are separate matters. My professor said the answer is true. I pressed him ...
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