Questions tagged [kinetics]
The study of rates and steps in mechanisms of chemical processes.
814
questions
2
votes
1answer
48 views
Effect of concentration on rate
How do I solve this question?
My thinking is this: since O2 is not a reactant in any step, and since the reaction rate depends only on the reactants, increasing the concentration of O2 does not ...
-1
votes
0answers
23 views
Rates of heterogeneous surface reactions [closed]
This is a question I've been trying to solve for a while, but I haven't taken chemical kinetics yet and just can't seem to figure it out. I have the following reaction:
$$\ce{CO2 + ^{\ast} <=> ...
-2
votes
0answers
20 views
Solving second-order kinetics [closed]
I have a chemical reaction: A + B --> P, where A and B react with a 1 to 1 stoichiometry to form product P.
The rate of change in concentration of A is given as: d[A]/dt = -k[A][B].
Similarly that ...
0
votes
1answer
34 views
Question on notation
Here, when they write $v/(\mathrm{mol\ s^{-1}\ (kg\ \text{protein})^{-1}})$ is $0.30$ for the first row first column, do they mean that the value is $0.30\ \mathrm{mol\ s^{-1}\ (kg\ \text{protein})^{-...
0
votes
0answers
34 views
Photoelectric effect question
My attempt:- 1)At 0.68e15 Hz frequency of light,Metal A gives 7.2eV Kinetic Energy(KE).
2)At 1e15 Hz frequency of light, Metal B, gives 6eV Kinetic Energy.
3) At 1.1e15 Hz frequency of light, Metal ...
-1
votes
0answers
15 views
Relation between rate of reaction and enthalpy [closed]
I came across a problem in which 2 reactions are carried out simultaneously inside an insulated container so that its temperature remains constant given that one reaction is endothermic while the ...
1
vote
1answer
27 views
Electron transfer rates in Marcus Theory [closed]
Electron transfer rates (k) as derived from Marcus theory assumes i) thermal equilibrium and ii) neglects quantum nature of low-frequency phonon modes. Can anyone explain what is at the heart of these ...
-2
votes
1answer
46 views
Is dimerization just a synonym for asscociation with n=2? [closed]
Association is a process of the form
$$\ce{nS<=>S_n}$$
Is dimerization refering to only the special case $n=2$ or is it synonymous for $n\in\mathbb{N}$?
-1
votes
1answer
27 views
Is it necessary that hydrolysis of ester will only take place in excess of water?
I was given a question on chemical kinetics in which the statement was given-
"The Concentration of water in hydrolysis of ester does not change to much extent"
I marked the statement to be false ...
-3
votes
1answer
52 views
I need explanation for reaction rate [closed]
That's a sample reaction:
$$2N_2+3O_2->2N_2O_3\ \ \ r=k_1[N_2]^2[O_2]^3$$
Why can't I write this as
$$N_2+\frac{3}{2}O_2->N_2O_3\ \ \ r=k_2[N_2][O_2]^{\frac{3}{2}}$$
Don't bother the elements. ...
2
votes
2answers
44 views
Is equilibrium constant at a given temperature derived from Gibbs free energy of reaction valid for doing simple kinetic modelling?
I intend to do a kinetic study of simple alcohol catalytic dehydrogenation reactions in the gas phase. I want to start with simple power law kinetics using $K_\mathrm{eq}$ to account for the ...
0
votes
2answers
45 views
Can I determine the rate law order from stoichiometric coefficients?
I've read in two books, and seen in three separate videos courses, that you cannot determine the rate law order from stoichiometric coefficients.
Then, I have seen homework and "practice" problems ...
2
votes
1answer
87 views
How to set up an equation to solve a rate law computationally?
I am confused on how to set up my equations to use in the solver. I have an equation
$$\ce{A + 2B -> C}$$
As a given, it is first order in A and second order in B. What I need to do is to solve for ...
1
vote
0answers
32 views
What is the activation energy of a Daniell cell?
I'm having trouble finding a posted literature value for the activation energy for the Daniell cell redox reaction:
$$\ce{Cu^2+ + Zn -> Cu + Zn^2+}$$
Where might I be able to find this ...
-2
votes
1answer
29 views
What is the molecularity of a reaction if it has a fractional order as per rate equation? [closed]
The rate equation of any reaction is found by using its slowest step.
My book says that molecularity of the slowest step of a reaction is equal to the order of the same reaction.
However, there are ...
2
votes
1answer
47 views
Rate of reaction involving different stoichiometric coefficients
Suppose I have a reaction (Say it is the Haber process):
$$\ce{N2 + 3H2 <=> 2NH3}$$
If we have to calculate the average rate of reaction of the above we follow the reasoning the rate of ...
0
votes
1answer
33 views
Rate determining step for parallel reaction?
I have always read that the rate determining step is the slowest step in a reaction (source: Wikipedia).
In chemical kinetics, the overall rate of a reaction is often approximately determined by ...
2
votes
0answers
22 views
Order of Reaction differs in equation and linearisation
I have given the following equation: $A + 2B \rightarrow C$
$ v = –k\cdot [A]\cdot[B]^2$
gives me the orders 1 for A and 2 for B. That results in a total order of the reaction of 3.
So far so good. ...
2
votes
2answers
35 views
How does the rate constant change with the change of the temperature?
In class, we discussed the following multiple-choice question.
The rate expression for a reaction is:
$$rate = k[X][Y]$$
Which statement is correct?
A. As the temperature increases, the ...
1
vote
1answer
55 views
How to derive the steady-state solution for simple two-step reaction with differential equations? [closed]
Consider this simple two step reaction, a variant of a Michaelis-Menten type of problem, where $\ce{A}$ and $\ce{B}$ reversibly bind to make $\ce{AB}$, and $\ce{AB}$ and $\ce{C}$ reversibly bind to ...
3
votes
2answers
133 views
General justification for steady state approximation
I want to understand the assumptions that have to be fulfilled in order for the steady state approximation to work. I did some research myself and was able to deduce assumptions of the form $k_1\gg ...
1
vote
3answers
49 views
Is the kinetic energy change of a system (q) equal to the enthalpy change of a system (∆H)?
When silver nitrate and hydrochloric acid are put together in a container, they form silver chloride. If you're given information about the reactants (including temperature change, heat capacity, and ...
2
votes
1answer
83 views
Why doesn't nitrogen react with oxygen at room temperature? [closed]
I already know that nitrogen's triple bond requires a lot of energy to be broken, so the activation energy is very high, but the book also lists the endothermic energy change as a reason.
Does the ...
0
votes
1answer
75 views
How to precipitate Chloroplatinic acid? [closed]
For the precipitation reaction, I have to react $\ce{H2PtCl6}$ with $\ce{(NH4)2CO3}$ while maintaining the $\ce{pH}$ in the range of 7-8 at 60 °C. But the problem is Chloroplatinic acid is not ...
0
votes
0answers
45 views
For a 1st order reaction, how do you derive the integrated rate law for a product versus time?
For a chemical reaction in which some stoichiometric quantity of arbitrary chemical $A$ decomposes into products $B$ and $C$,
$$a \ce{A} \ce{->} b \ce{B} + c \ce{C}$$
or more simply:
$$a\ce{A} \...
3
votes
2answers
59 views
Deriving rate law from a reaction mechanism for a chain reaction using steady-state approximation
I am trying to derive the overall rate equation for the photocatalysed halogenation (chlorination) of an alkane that proceed via this 4 step chain reaction:
$\ce{Cl2->2Cl^. \quad(1) initiation}$ ...
0
votes
2answers
72 views
Unusual Result in Kinetics Lab
The question: In the lab described below, why did the decolorization reaction described, which should be first order in each of the two reactants, go most slowly when the reactants were most ...
3
votes
3answers
484 views
Can I express the rate of a reaction as percent per second (%/s)?
Rate is calculated as change in concentration over change in time, so usually $\pu{M/s}$ $(\pu{mol L-1 s-1}).$
Say, I'm calculating it for $20\%$ solution of ammonium hydroxide, so my final rate is ...
1
vote
0answers
76 views
Controlling rate of endothermic reaction
In an experiment, I have two endothermic reactions taking place simultaneously:
$$
\begin{align}
\ce{A + B &-> C + D}\tag{1}\\
\ce{E + G &-> Z + F}\tag{2}
\end{align}
$$
$\ce{C}$ and $\...
1
vote
1answer
18 views
R and T conformations in relation to Activators and Inhibitors; Km of reaction in relation to uncompetitive and non-competitive inhibitor
Do
-Activators
-Competitive Inhibitors
-Non-Competitive Inhibitors
-Uncompetitive Inhibitors
all change the conformation of the targeted enzyme from T to R (activator), and from R to T (the rest) ...
1
vote
2answers
48 views
Does the concentration of water accounts for determining the rate of a reaction?
I found this problem in my book and I'm not sure how to assess this question.
It is as follows:
Regarding the relationship between the rates of the chemical species
in the following reaction. ...
-1
votes
2answers
96 views
What is the rate equation of decomposition of H2O2 with catalysts?
What is the rate equation of this reaction with the presence of catalysts $\ce{MnO2}$, $\ce{PbO2}$ and $\ce{Fe2O3}$? (asking for each of them, separately, not altogether)
$$\ce{2H2O2 -> 2H2O + O2}$...
8
votes
2answers
988 views
If a reactant appears on both sides of an elementary equation, can it be cancelled?
Me and a friend were debating the following. For the elementary reaction
$$\ce{A + B -> A + C}$$
my friend says that it is unimolecular because $\ce{A}$ does not "participate" in the reaction. So,...
0
votes
0answers
22 views
Can the relative reactivities of different compounds that undergo the same reaction be compared if the compounds follow different overall kinetics?
I have read that if some different compounds undergo the same reaction and under the same conditions, but follow different overall kinetic orders, then their rate constants or relative reactivities ...
3
votes
2answers
59 views
Preparation of Barium Hexaaluminate using co-precipitation reaction mechanism
I am preparing Barium Hexaaluminate (BHA) using $\ce{Ba(NO3)2, Al(NO3)3}$, and $\ce{(NH4)2CO3}$. For $\pu{1 mol}$ of each $\ce{Ba(NO3)2}$ and $\ce{Al(NO3)4}$, I am using $\pu{1.5 mol}$ of $\ce{(NH4)...
1
vote
1answer
47 views
Writing a system of differential equations with the given arbitrary reactions
We have the following elementary reactions:
\begin{align}
&\overset{k_1}{\longrightarrow}A\overset{k_2}{\longrightarrow}{B+C}\\
&C \overset{k_4}{\longrightarrow} 2D \overset{k_5}{\...
3
votes
1answer
37 views
A “function of proportionality” in a rate law [closed]
I am currently studying rate laws and the determination of the order of a reaction. So first-order reactions remind me of linear functions $f(x)=kx$ while second-order reactions remind me of quadratic ...
0
votes
0answers
27 views
How does the temperature affect the frequency factor?
I am a high school student and have been trying to learn how the temperature affects the frequency factor. I did not even understand the equation below, which is from this site. Can anyone please ...
0
votes
1answer
62 views
Are the reaction rates of these equations equal? [closed]
$$\ce{CH3CH2CH2Br + OH- -> CH3CH2CH2OH + Br-}$$
$$\mathrm{rate} = k[\ce{CH3CH2CH2Br}][\ce{OH-}]$$
If I change the $\ce{Br}$ with any element from halogens (without changing concentration, volume, ...
2
votes
0answers
32 views
Using calculus to find the rate of a bivariate reaction
Recently, I've been learning about rates and have found the concept fairly easy to understand in the case of a reaction with a single reactant, which is essentially solving $$f'(t) = kf(t)^n$$ where $...
3
votes
1answer
59 views
The reaction rate when the rate-determining step has a back reaction
For some reason, I am reviewing general chemistry and I find that the elementary reaction for the rate-determining step (RDS) is assumed to be irreversible, that is, single arrow, in all questions ...
0
votes
1answer
33 views
Sum of a rate constant gives the total decay rate
I want to ask a question about the sum of a rate constant to yield the total decay rate.
From previous studies, the rate of a reaction can be expressed evidently as
$$\ce{v_{rate} = k[A]}$$
where ...
1
vote
0answers
42 views
Rate determining step in oxidation of alcohols using chromium-related compounds
I wanted to ask a question about the kinetics of an oxidation reaction using chromium reagents.
I was given a lecture today on the mechanism of alcohol oxidations using Chromate (VI) reagents:
My ...
0
votes
1answer
53 views
How much oxygen is formed in this first order reaction? [closed]
We have a reaction
$$\ce{2N2O5 -> 4NO2 + O2},$$
which has a rate constant $k=6,2\cdot10^{-4}/\mathrm{min}$ at temperature $T=318.15\ \mathrm{K}$. How much oxygen is formed in litres when $1.00\ \...
1
vote
0answers
72 views
Literature value for the activation energy of the reaction between hydrochloric acid and sodium bicarbonate
Does anybody have the literature value for the activation energy of the reaction between hydrochloric acid and sodium bicarbonate? If yes, could you please cite the source for it and the value?
I ...
1
vote
0answers
43 views
Why do the NMR peaks shift when H+ concentration and temperature are varied on the reversible hydrolysis of pyruvic acid to 2,2-dihydroxypropionate? [closed]
We performed two experiments. Each of the peaks are referring to the methyl peaks in both reactant and product of the hydrolysis reaction.
We varied $\ce{H+}$ concentration of the reaction and the ...
1
vote
0answers
155 views
Order of reaction in adsorption process
(1) $\ce{PH3(g) <=>[W]PH3(adsorption)->[W]P(s) + 3/2 H2(g)}$
The decomposition of phosphine on tungsten surface at low pressure is a pseudo first order reaction. This is because the rate of ...
0
votes
0answers
26 views
Convert to NASA polynomial format for chemical kinetic calculations
I have calculated thermodynamic properties of a metal oxide through DFT calculations, I want to convert it to NASA polynomial format and use those thermodynamic properties along with rate constants ...
0
votes
1answer
49 views
Order of reaction for hydrogen ions being ignored
I have been reading through a case study about calculating the order of reaction for the following reaction:
$$\ce{H2O2 + 3 I- + 2 H+ -> I3- + 2 H2O}$$
The paper uses an iodine clock reaction ...
0
votes
0answers
34 views
Why do statistical effects impact stepwise stability constants?
I have a question regarding the stepwise stability constants of metal complex formation/substitution.
My lecture notes say that if we have a metal complex, say $\ce{[MX_{6}]}$, and a substitution ...
