What is Chemical kinetics: Definition and 46 Discussions
Chemical kinetics, also known as reaction kinetics, is the branch of physical chemistry that is concerned with understanding the rates of chemical reactions. It is to be contrasted with thermodynamics, which deals with the direction in which a process occurs but in itself tells nothing about its rate. Chemical kinetics includes investigations of how experimental conditions influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition states, as well as the construction of mathematical models that also can describe the characteristics of a chemical reaction.
Hi,
I'm following an introduction course to chemistry and I am reviewing the chapter on Chemical kinetics.
It's shown that the reaction speed for a certain component of a general chemical equation such as aA +bB <> cC + dD , might be expressed as v = k[A]m[ B]m.
I was wondering where it does...
last week i did a chemistry lab. i mixed NaOH 0.03M with equal part of methyl violet and mesured aborbance in a spectrophotometer. then i did the same thing with a 0.05M and methyl violet
i did today the graphs and got the k' =0.1647 for the first solution and k'=0.4022 for the second...
We are required to design a facility to produce hydrogen via Sulfurammonia cycle making use of the solar spectrum with long wavelength spectral composition to drive thermal processes and short wavelength composition to drive the hydrogen producing using photolysis. Also, I must use the...
Homework Statement
Two mechanisms are proposed (as seen in the screenshot). Which mechanism and which step as the rate determining step would best fit the data?
Homework Equations
I think this is more of a conceptual problem ...
The Attempt at a Solution
I apologise for not strictly...
Hi everybody,
Given a generic reaction ## Reagents ↔ Products ## the velocity of the reaction is ##R = R_{right}  R_{left} ##
To take in account that the velocity of the reaction will slow if approaching the equilibrium we say that
$$ R = R_{right}(1  \frac K K_{eq}) $$
Although it seems...
Hey!
I have a question regarding this question that I have to answer. It is about the kinetics of a substance X whose product is 2Y. It is in Swedish and here is the translation:
The absorbance of a 0,030Msolution of X was calculated with the help of a Spectrometer. The Spectrometer was...
Homework Statement
Homework Equations
Is the question asking the concentration when the system has reached its half life
Can use the half life formula?[/B]The Attempt at a Solution
So
1/cT + 1/co = kt
1/(4 *102) + 1/x = k(half life time)
Is this the right approach
Please help me...
Homework Statement
The task is the following:
If the concentration of A decreases 0.03 M in one hour, then the concentration of B should to, which means, [ B] should be 0.05 M?
And if I try to calculate k, i get 14.87 l/(mol*h)
For second order reactions, t1/2 sould be 1/(k*[A]0)
So I get...
Good evening, people of PF. Recently, while studying chemical kinetics, I have come across some questions about reaction rates and rate equations. I've noticed some inconsistencies between the chemical kinetics point of view, and the approach taken by chemical reaction engineering and reactor...
Homework Statement
There was a statement in a question which said:
"The order of an elementary chemical reaction step can be determined by examining its stoichiometry. "
And it was given correct.
Homework EquationsThe Attempt at a Solution
But shouldn't it be wrong? Order of a reaction is...
Homework Statement
The rate of the reaction was studied at a certain temperature.
O(g) + NO2(g) > NO(g) + O2(g)
In the first set of experiments, NO2 was in large excess, at a concentration of 1.0 * 10^ 13 molecules/cm3 with the following data collected.
time (s) [O] (atoms/cm3)
0...
Homework Statement
I'm just rewording the question, because there is one thing in particular I'm after.
Given a graph of A, B, & C in Concentration(y) versus time(x), can you determine the balanced chemical equation?
Is that possible? I guess if you found the rates and then checked to see...
Homework Statement
The second order reaction 2Mn(CO)sub5 → Mnsub2 (CO)sub10 has a rate constant equal to
3.0 *10^9 M^1s^1 at 25oC. If the initial concentration for Mn(CO)sub5 is 1.0 * 10^5 M, how long will it take for 90% of the reactant to disappear?
Homework Equations
Rate Law =...
X + Y + Z > A + C+ + B
Initial Concentrations Z= 4.1 X 10^3M, X=2.3 X 10^1M, Y= 1.2 X 10^1 M.
http://s121.photobucket.com/user/marykaywest420/media/81386cf6e13245788fb51024a2a3f3d5_zpscc804723.jpg.html?sort=3&o=0
3. So my attempt included graphing R/(R∞R) vs. time. which produced...
Homework Statement
Good day! I have a question from my chem HW that is stumping me. Although the answer may be simple, it has eluded me for quite a bit. It regards rate laws and constants of reactions.
Question is as stated: This reaction was monitored as a function of time: AB > A + B
A...
Homework Statement
Homework Equationsln[A]=kt+ln[A]0
The Attempt at a Solution
In this equation,is it necessary to have [A] to be the concentration?
If there is the mass provided only,can I just subsitute [A]=mass?
Sorry for my poor english
My textbook (Burdge, Chemistry, 2nd edition) is pretty vague mathematically when it comes to calculating the examples, so I'm a bit confused about solving this example problem.
The equation is fairly straightforward:
ln{[A]_{t}/[A]_{0}}=kt
The 14.4 problem statement is (paraphrased)...
Homework Statement
The mean life of a certain radioactive element is 6 hrs. By what fraction will its initial activity decrease over a time period of 5 hrs.
Homework Equations
t_{avg}=\frac{1}{k}
Initial Activity = kN_{0}
Final Activity = kN_{t}
The Attempt at a Solution
From eqn 1...
Homework Statement
So the question says
for the reaction 2N2O5(g) > 4NO2 (g) + O2(g) provides a linear plot when P(N205) is plotted against t with a negative slope . The decomposition of N2O5 follows ?
Homework Equations
The Attempt at a Solution
I am guessing that P(N205) is...
a mixture of two miscible liquids a nd b has 10 moles of a and 12 moles of b. pure vapour pressure of a is 300mm Hg and tht of b is 500mm of hg. as soon as b is added to solution A starts polymerising into an insoluble solid. after 100 minutes 0.525 moles of a solute C is added whch stops...
The correct answer states its C which i understand why since doubling the intiial volume of SO2 is equivilent to doubling the intial moles of SO2 hence the moles of SO3 produced will also increase and hence pressure exerted shld be higher than before which is not reflected by the graph...
The problems are Number 12 and 13 on this link
http://isites.harvard.edu/fs/docs/icb.topic1096438.files/PS4.pdf
I have the value of k for sum number 12, it is 1.54*10^4.
Im completely stuck with number 13 cos I'm unfamiliar with that concept and it kinda went over my head in lecture...
I am studying the activation energy of a reaction, and I notice that it says when the products are more stable than the reactants the reaction is exothermic, and endothermic when the products are less stable than the reactants.
It doesn't say why, but my supposition is that when the products...
Hi everyone
Homework Statement
I got the three different diagramms (attached below) and I shall find a general chemical equation for all of them.
Homework Equations

The Attempt at a Solution
I think I know how to do the third one, but I have troubles with the first...
2NO + 2H2 > N2 + 2H2O
The concentration of NO is 0.006 M and the concentration for H2 is 0.002M. How can I find the concentration of NO remaining when onehalf of the original amount of H2 has been consumed?
if you can also show me how it would be done if the reaction was not 1:1, that...
Homework Statement
At 25 C a catalyzed solution of formic acid produces 44.6 ml of carbon monoxide gas in 30s.
a) Calculate the rate of reaction with respect to CO(g) production.
Homework Equations
Rate = dC / dT
The Attempt at a Solution
dC should be expressed in mol/L but I...
Homework Statement
2HCl + Na2S2O3 > 2NaCl +S + SO2 + H2O
Find the order of reaction with respect to S2O32 and H+
volume of 3.0M HCl was held constant at 2ml
Homework Equations
S2O32 + 2H+ > S + SO2 + H2O
rate = k[Na2S2O3]m[HCl]n (see number 3.)
The Attempt at a Solution
i just...
In my textbook there is an example with the following reaction and rate:
C6H6 + 3H2 > C6H12
Rf = kf[C6H6][H2]
Then the the example claims that the ratio of the rate constants is:
kf / kr = [C6H12] / ( [H2]3 [C6H6] )
How is the denominator of that ratio possible if the forward...
Homework Statement
Consider a first order decomposition reaction
2P(g) > 4Q(g) + R(g) + S(l)
taking place at a temperature T. After 30 minutes from the start of the decomposition in a closed vessel, the total pressure developed is found to be 317 mmHg and after a long time, the...
So, let's say we have an elementary reaction:
2A > C
The rate of this reaction is (according to IUPAC: http://goldbook.iupac.org/R05156.html)
 \frac{1}{2} \frac{d[A]}{dt} = k [A]^2
If we integrate this we get a certain integrated rate law (second order)
However, if we multiply all of...
Homework Statement
Our chemistry teacher just learned about chemical kinetics. I've been working with the calculus teacher to find out how to determine instantaneous rates exactly. We don't have any equation. Could someone explain this please?
Homework Equations
The Attempt at a...
Homework Statement
I understand how to determine the order of a rxn based on a series of experiments one divides one into another to obtain a ratio and then determines the power to which one is raised to determine the order.
Typical data collected would be:
Ex1 [A] .2 mol = Initial rate...
I am having a problem with my kinetics lab. There are just three questions I can not understand.
1. Determine the order with respect to HCl. Explain.
2. Determine the order with respect to Sodium Thiosulfate. Explain.
3. Why rate values for this experiment not adequate to achieve an accurate...
Can anyone please explain to me what is reaction mechanisms and intermediate? I have read my book many times, but I don't get it. Also, it would be great if you can me some examples about them. Thank you for your help!
Homework Statement
1. According to the mechanism below, what is the correct expression for the rate of consumption of A? In the mechanism, M is a molecule that collides with A and A* is a highlyenergized form of A.
Step 1 (reversible): A + M <> A* + M rate constants k1 and k1
Step...
Homework Statement
1. According to the mechanism below, what is the correct expression for the rate of consumption of A? In the mechanism, M is a molecule that collides with A and A* is a highlyenergized form of A.
Step 1 (reversible): A + M <> A* + M rate constants k1 and k1
Step...
I've been independantly studying chemical kinetics from a standard freshman year chemistry textbook, and I enjoy the subject, could anyone suggest any further reading or sources? Specifically I'd like to try and find a calculus based text, as the one I have specifically avoids using any...
Homework Statement
Write down the material balance for the components A, B, C, D id this reaction takes place in a batch reactor:
A+B\UpdownarrowC and C+B\UpdownarrowD
The difunctional starting material (A) combines with the primary reactant (B) to form a monofunctional intermediate (C)...
Hello everyone,
I am having trouble with determining where I erred in the following exercise. If someone could point out my mistake, I would appreciate the help.
Thank you!

1. The decomposition of N2O5 has an activation energy of 103 kJ/mol and a frequency factor of 4.3E13 s^1 . What...
Homework Statement
This is straight off an old AP Exam, but I can't seem to find it online so I'm hoping you all can help me out.
2 NO(g) + Br2(g) > 2 NOBr(g)
The following results were obtained in experiments designed to study the rate of the reaction above.
Experiment Initial...
Hello,
I have the following mechanism:
NO + NO > N2O2
and
N2O2 + H2 > N2O + H2O
We need to identify intermediates in the mechanism. I have no idea how to do that.
In case it helps, here are the answers (not sure they are right, but I think they are) to previous questions in the...
Hello everyone,
I have been working on several exercises for the past several days, and there are some I just can't seem to do. I would appreciate some help! =)
1) We have the following reaction: C2H5Br (alc) + OH() (alc) > C2H5OH (l) + Br()
The () indicates it's an ion.
The...
We are currently studying reactions in terms of kinetic energy, reaction rates, collision theory, and so on.
There is a question on my assignment that is kind of boggling me right now:
An increase in temperature of 10 C rarely doubles the kinetic energy of particles, and hence the number...
HI
While working on some chemical kinetics problems, I came across the statement, the fraction of activated molecules is 10^{15} in a problem where some other constants were also provided and the half life was to be found (for a first order reaction). My specific query is:
Is this...
The rate constant for a certain reaction has the units concentration/time. What is the order of the raction?
A. 0
B. 1
C.2
D.3
My reasoning:
K = [A]^m x [B]^n
Since the concentration/time is to the power of one, both m and n must be one i think which give an overall order of...