Questions tagged [kinetics]
The study of rates and steps in mechanisms of chemical processes.
957
questions
2
votes
1answer
57 views
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
$$\...
0
votes
0answers
19 views
Temperature at which the reaction Oxalic acid + KMnO4 becomes autocatalytic
As described many times, the reaction between oxalic acid and potassium permanganate can be autocatalytic due to the production of Manganese ions.
I've read that this only occurs at higher ...
0
votes
1answer
34 views
Does mass affect rate of reaction?
Suppose I am reacting HCl with CuCO3.
Experiment 1: I use 2g powdered CuCO3
Experiment 2: I use 4g powdered CuCO3
All other variables are kept constant.
Will this have any affect on rate of reaction? ...
-1
votes
0answers
37 views
Why is the rate of absorption constant? [closed]
In a comparison between absorption and adsorption, absorption was stated to take place at a constant rate, as opposed to adsorption, which slows down as the system reaches equilibrium.
How does ...
4
votes
2answers
64 views
Determine vmax and enzyme concentration (Michaelis–Menten)
I am given that the enzyme concentration is $\pu{15 nM}$ and the following data:
$$
\begin{array}{rl}
\hline
S/\pu{mM} & V/\pu{mM s^{-1}} \\
\hline
1 & 0.202 \\
2 & 0.368 \\
5 & 0....
-2
votes
0answers
19 views
Chemistry volume question [closed]
*Oxygen has 24 dm3 of volume at room temperature and pressure
1)What would happen to this volume of gas in terms of the kinetic theory if the pressure is kept decreased and the temperature is ...
0
votes
0answers
19 views
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 $\ce{H2}$ ...
1
vote
1answer
93 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 ...
-3
votes
0answers
24 views
Why does According to Le-Chateliers principle, adding heat to solid and liquid in equilibrium will cause the amount of solid to decrease
According to Le Chatelier's Principle the external changes must be counteracted but in this scenario the external factors causes the amount of solid to decrease because of obviously melting but if Le ...
1
vote
0answers
40 views
How does the rate constant vary double by doubling the concentration of a reactant?
Rate law for the reaction, $\ce{A +2B-> C}$ is found to be, Rate $\mathrm{=k[A][B]}$
The concentration of reactant $\ce{'B'}$ is doubled, keeping the concentration of $\ce{'A'}$ constant, the value ...
6
votes
1answer
197 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 $\mathrm{rate} = k[\ce{X}]$?
2
votes
0answers
32 views
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 ...
2
votes
2answers
40 views
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?...
4
votes
0answers
43 views
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 ...
-1
votes
0answers
17 views
What is the activation energy of the landolt reaction (iodate variation of the iodine clock reaction)? [duplicate]
I cannot find it anywhere for the life of me. If you can help me in anyway whatsoever even imply guiding me to something useful I would appreciate it greatly.
3
votes
1answer
68 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 ...
1
vote
0answers
24 views
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 ...
0
votes
0answers
27 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 ...
0
votes
1answer
35 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 ...
2
votes
0answers
49 views
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 ...
2
votes
1answer
49 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 $\pu{2.0 L}$ ...
1
vote
0answers
52 views
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 ...
4
votes
3answers
91 views
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 ...
0
votes
0answers
27 views
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 ...
3
votes
0answers
22 views
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 ...
7
votes
3answers
329 views
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.
$K_{M}$ ...
1
vote
0answers
33 views
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]$_0$
$$\ce{I^- + H_2O_2 -> I_2}$$
$$\ce{I2 + ascorbic acid -> I- + side products}$$
...
4
votes
1answer
80 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\ & ...
2
votes
1answer
26 views
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 ...
2
votes
0answers
40 views
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, ...
1
vote
0answers
37 views
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-...
3
votes
1answer
58 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 ...
-1
votes
0answers
16 views
What are some different ways of finding the activation energy of a reaction?
One method that I know that works is observing the half-life of a reaction, another involves measuring the time and concentration and calculating the time at which half of the original concentration ...
4
votes
0answers
29 views
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 ...
-1
votes
1answer
66 views
Sequential reaction in equilibrium
Derive an equation for the steady-state rate of the sequence of reactions $$\ce{A <=> B <=> C <=> D}$$ with $[\ce{A}]$ maintained at a fixed value and the product $\ce{D}$ removed as ...
2
votes
1answer
48 views
Is Km the concentration needed to keep the enzyme running at max speed?
$K_m$ is the Michaelis constant, which is the concentration of substrate needed to achieve a rate of $\frac{V_{max}}{2}$. $V_{max}$ is the maximum number of molecules that can be reacted per second.
...
0
votes
0answers
33 views
Michaelis–Menten kinetics applied to a solution with two enzymes
Two enzymes are added to a solution containing a tow concentration of a substrate that they can both use. Which statement is correct?
A. Both enzymes will use equal amounts of the substrate.
B. ...
3
votes
3answers
106 views
Finding reaction rate constant for second order equation in Wolfram Mathematica [closed]
I’m working in Mathematica for my master’s project and I can’t work out how to find $k$ in the second order rate equations where I have a concentration vs time graph for $\ce{AHA}:$
$$\mathrm{rate} = ...
4
votes
0answers
49 views
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 ...
1
vote
0answers
38 views
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 ...
3
votes
1answer
79 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 ...
2
votes
0answers
55 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 ...
4
votes
0answers
22 views
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 ...
3
votes
0answers
22 views
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,...
4
votes
2answers
374 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 ...
4
votes
1answer
58 views
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 ...
5
votes
4answers
233 views
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 $...
0
votes
0answers
44 views
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 ...
3
votes
0answers
28 views
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 ...
0
votes
0answers
46 views
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 ...
