Questions tagged [kinetics]

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

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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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324 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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203 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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221 views

Should rates and rate constants be expressed in terms of pressure or concentration?

If an elementary reaction was conducted in the gaseous phase, say $$\ce{X (g) -> Y(g)},$$ would the formal definition of the rate law be $\mathrm{rate} = kP_\ce{X}$ or $\mathrm{rate} = k[\ce{X}]$?
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Lindemann-HInshelwood mechanism difference between high and low concentration

I have a gas reaction which follows the Lindemann-Hinshelwood mechanism and want to calculate the rate constant at low and at high concentrations of the gas but I find myself stuck at what my next ...
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How can you qualitatively tell when the hydrolysis of aspirin is over?

I'm doing an experiment on the effect of temperature on the time taken to produce acetic acid and salicylic acid. Are there any qualitative observations I can make about when the reaction has finished?...
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Lindemann–Hinshelwood mechanism for a gas reaction

The effective rate constant for a gaseous reaction which proceeds by a Lindemann–Hinshelwood mechanism is $\pu{1.01E-5 s^-1}$ at a concentration of $\pu{4.6E-6 M}$ and $\pu{2.21E-5 s^-1}$ at a ...
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297 views

Is the rate of a zero order reaction always independent of the concentration of its reactants?

Consider the following reaction : $\ce{A + B}$ $\rightarrow$ $\ce{Products}$ where order of the reaction w.r.t. $\ce{A}$ is $-1$ and order of the reaction w.r.t. $\ce{B}$ is $+1$. So, overall order of ...
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Why on changing temperature of a reaction its activation energy and pre-exponenetial factor do not change significantly?

My teacher told me that on changing temperature of a reaction, its activation energy ($E_{a}$) and pre-exponenetial factor ($A$) do not change significantly and hence we can assume them to be constant ...
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56 views

What is the literature value of the activation energy of the reaction between iodate and bisulfite?

I explored the Arrhenius equation using the reaction between potassium iodate (containing the IO3- iodate ion) and sodium metabisulfite (bisulfite ion), however I can't find a literature value to draw ...
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140 views

Why catalyst does not alter the entropy of a reaction?

In my textbook it is written that "Catalyst does not alter the entropy of a reaction". But why? There is literally no explanation given in my textbook as to why this is true. Could you ...
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Why is the variable on the y-axis of Maxwell's Speed Distribution Curve 'fraction of molecules'?

I came across the following graph in my textbook showing the kinetic energy distribution of the gas molecules in a gas sample. Now, the thing is the textbook is telling that the area under the curve ...
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1answer
53 views

Finding half-life of a nuclide based on gas release

Full Question: The hydride of an unstable nuclide of a Group IIA metal, $\ce{MH2 (s)}$, decays by alpha emission. A $\pu{0.025 mol}$ sample of the hydride is placed in an evacuated $\pu{2.0 L}$ ...
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Confusion in thermodynamically and Kinetically controlled reaction

I am confused in following reaction: $\ce{(CH3)2CH-CHO}$ when reacts with conc. $\ce{NaOH}$, will it undergo cannizaro reaction? According to our professor, It can undergo both Cannizzaro as well as ...
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If all molecules have basically the same KE at a given temperature, why do lighter isotopes evaporate more readily?

One of the proxies used for paleoclimate is the ratio of oxygen-18 to oxygen-16 in ice cores and in sedimentary rocks. The idea is that water molecules with oxygen-18 generally evaporate less readily ...
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Measuring energy required or generated in gasification

The typical equation used to measure heat is as follows: $q = mcΔT\\ \text{Where, }\\ q = \text{heat} (\pu{J}) \\ m = \text{mass} (\pu{g}) \\ c = \text{specific heat capacity} (\pu{J g^-1 K^-1})\\ ΔT ...
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Why does allosteric binding produce a sigmoidal curve?

Allosteric binding is where the enzyme can be regulated through having ligands bind onto somewhere that is not the active site. This will then induce a conformational change on the active site, hence ...
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Why use Km in catalytic efficiency?

The catalytic efficiency of an enzyme is given by $k_{cat}/k_M$ where $k_{cat}$ is the turnover number, or the number of molecules that can be produced per second per active site of an enzyme. $K_{M}$ ...
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Does the rate reaction of clock reaction increase over time?

I'm studing the following version of iodine clock reaction, in which, $[\ce{H_2O_2}]_0$ > [ascorbic acid]$_0$ $$\ce{I^- + H_2O_2 -> I_2}$$ $$\ce{I2 + ascorbic acid -> I- + side products}$$ ...
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198 views

Determine reaction order and reaction rate

In a solution of $\ce{Fe^3+}$ the concentration was measured to be: $$\begin{array}{c|c} t/\pu{min} & \ce{[Fe^3+]}/\pu{\mu M} \\ \hline 10\ & 238\\ 20 & 227\\ 40\ & 206\\ 60\ & ...
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Diffusion of multiple gases at once

Graham’s law of diffusion states the rate of diffusion between two gases is inversely proportional to their molar masses. Now, this is helpful when we are focused on two gases. But that is rarely the ...
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Effect of stirring and shaking on chemical kinetics

Why don't we take the effects of stirring and shaking on the rates of chemical reactions? While studying chemical kinetics, I've seen that the rates depend on the concentrations of various species, ...
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Using the steady state approximation in the decomposition of nitramide to determine rate law

$\ce{O2NNH2 (aq) ->[\mathit{k}_1] O2NNH- (aq) + H+ (aq)}$ $\ce{O2NNH- (aq) + H+ (aq) ->[\mathit{k}_{-1}] O2NNH2 (aq)}$ $\ce{O2NNH- (aq) ->[\mathit{k}_2] N2O(g) + OH- (aq)}$ $\ce{H+ (aq) + OH-...
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70 views

Are the orders of reactants with respect to a reaction different for different starting concentrations?

If the reaction is repeated with $\pu{2 M}$ ethyl iodide the pyridine concentration decreases as shown below. Give the rate law of the reaction in terms of pyridine and ethyl iodide. Explain your ...
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What do the phase space and slope fields of the iodine clock reaction look like?

The iodine clock reaction is a fun experiment shown to undergraduates to illustrate that chemical reactions can show periodic behaviour. Presumably, or hopefully, there is a system of differential ...
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136 views

Sequential reaction in equilibrium

Derive an equation for the steady-state rate of the sequence of reactions $$\ce{A <=> B <=> C <=> D}$$ with $[\ce{A}]$ maintained at a fixed value and the product $\ce{D}$ removed as ...
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51 views

Is Km the concentration needed to keep the enzyme running at max speed?

$K_m$ is the Michaelis constant, which is the concentration of substrate needed to achieve a rate of $\frac{V_{max}}{2}$. $V_{max}$ is the maximum number of molecules that can be reacted per second. ...
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Michaelis–Menten kinetics applied to a solution with two enzymes

Two enzymes are added to a solution containing a tow concentration of a substrate that they can both use. Which statement is correct? A. Both enzymes will use equal amounts of the substrate. B. ...
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117 views

Finding reaction rate constant for second order equation in Wolfram Mathematica [closed]

I’m working in Mathematica for my master’s project and I can’t work out how to find $k$ in the second order rate equations where I have a concentration vs time graph for $\ce{AHA}:$ $$\mathrm{rate} = ...
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Decomposition of Hydrogen Peroxide Catalysed by Potassium Iodide in Basic Solution

As part of my high school project, I had to measure the initial rate of decomposition of hydrogen peroxide catalysed by potassium iodide at different pHs. At higher pHs (alkaline conditions), I found ...
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How much energy is required to operate a Sabatier Reactor?

I'm trying to model some industrial processes and having a hard time finding information about the Sabatier reaction. The sabatier reaction combines CO2 (and possibly CO) with H2 to produce H2O and ...
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326 views

p-Nitroaniline reaction with sulfuric acid

An alternative version of the well-known demonstration carbon snake (the dehydration reaction of sugar by concentrated sulfuric acid forming a column of graphite) consists in mixing paranitroaniline ...
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87 views

Hydrogen peroxide and potassium iodide reactions

What is the explanation for the two possible reactions of $\ce{H2O2}$ with $\ce{KI}$ in acid media (iodide-catalyzed decomposition of hydrogen peroxide or iodide oxidation by hydrogen peroxide) and ...
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Normalising Kinetic Isotope Effect Per Deuterium Atom

I've synthesised a protic and deuterated version of a specific molecule where there are two deuterium atoms in the latter. I then go about and measure the kinetic isotope effect (KIE) for a reaction ...
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Differences in AChE inhibition kinetics between VX and VR

According to the referenced paper, VR has an AChE inhibition reaction rate constant almost 4 times that of VX. Interestingly, its reaction rate constant for aging of the enzyme is less than that of VX,...
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428 views

Why does denaturation of albumen protein cause pH of solution to increase?

I'm interested in the denaturation of proteins by alcohols, specifically by ethanol. I have devised a simple experiment in which I inject solutions of ethanol (of variable concentrations) into ...
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Propagating uncertainty with the slope of a tangent line

I have done an experiment that found the initial reaction rate for a reaction that created gas in $\pu{kPa s^-1}$ by finding the slope of the tangent line at time = 0. How do I propagate uncertainty ...
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Formula for rate constant for the first order reaction

My lecturer mentioned that the formula for the rate constant $k$ for the first order reaction is $$k = \frac{2.0303}{t_{1/2}}\,\log\frac{[\ce{A}]_0}{[\ce{A}]_{t_{1/2}} - [\ce{A}]_0},\tag{1}$$ where $...
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Finding rate constant from a change in pressure experiment

I measured the change in pressure for the decomposition of hydrogen peroxide in the presence of a manganese(IV) oxide catalyst at 5 different temperatures: $$\ce{2 H2O2 (l) ->[MnO2 (s)] O2 (g) + 2 ...
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Is it feasible to calculate the rate law of the oxidation of ethanol using colorimetry?

My IB Chemistry class needs to have our Internal Assessment ideas finalized by next week, and I'm torn between a few experiments. I'm considering performing an oxidation of ethanol and potentially ...
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What happens when solution containing two or more cations are electrolysed at an excess potential?

$\pu{250 mL}$ of a waste solution obtained from the workshop of a goldsmith contains $\pu{0.1 M}$ $\ce{AgNO3}$ and $\pu{0.1 M}$ $\ce{AuCl}$. The solution was electrolyzed at $\pu{2 V}$ by passing a ...
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Steady State: Exclusion of Term

Synopsis We are given a proposed mechanism for the condensation of $\ce{(CH_3)_2CO}$ as follows First Step: $$\ce{(CH_3)_2CO + OH^- <=> CH_3C(O)CH_2^- + H_2O}$$ Second Step: $$\ce{CH_3C(O)CH_2^- ...
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64 views

Activity of Polonium in half-time in Becquerels

I got an exercise but I don't know the exact answer. In the catalog note of the reference source of Polonium-210 radiation with a half-life of 138 days, it was stated that one day the activity was $\...
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131 views

Why a catalyst is not consumed in a reaction when all steps are reversible?

It is said that a catalyst speeds up the rate of a reaction but is not consumed (assuming no side reactions take place). Suppose we have the following reaction: $$\ce{A + B <=> C} $$ catalysed ...
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232 views

Equilibrium constant of a reaction whose order of forward and reverse reaction is not same

Suppose, a reaction is like, $$\ce{aA + bB <=> cC + dD}$$ and that A, B, C, D all are gas. Now it is known that: $$K_c = \dfrac{[A]^a[B]^b}{[C]^c[D]^d}$$ Now if the forward reaction is second ...
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92 views

Why does chemisorption decrease with increasing temperatures?

Why is it that chemisorption decreases with higher temperatures? The explanations I found online were quite vague and one of them cited Le Chatelier's principle, but I thought chemisorption is an ...
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Is standard change in activation Gibbs free energy indepedent of pressure?

For a chemical reaction the activation volume is defined as: $$Δ^{\ddagger}V={V^\ddagger}-V$$ where both $V^\ddagger$ and $V$ refer to standard states (I have omitted the symbol for simplicity). One ...
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26 views

kinetic description of an autocatalytic system

I have previously asked this question at physics SE here and it was suggested to post it here. I am looking at the system: $2X + Y \Leftrightarrow 3X $ $A \rightarrow Y$ $X \rightarrow B$ The ...
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75 views

Why are the "extents of reaction" the same for all reactants and products?

Consider the follwoing reaction: $$\ce{a A + b B -> c C + d D}\tag{1}$$ where $\ce A$ and $\ce B$ are the reactants, $\ce C$ and $\ce D$ are the products, and $a (<0)$, $b(<0)$, $c(>0)$, ...
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172 views

New relationship between exponential factors and entropy of a reaction?

Consider the reaction $\ce{A <=> B}$. Let $k_f$, $E_A$, and $A$ denote the forwards rate constant, activation energy, and pre exponential factor, respectively. Let $k_r$, $E_A'$, and $A'$ denote ...

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