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.

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  1. Ale_Rodo

    What's the derivation of the 'Kinetic Equation' in Chemical kinetics?

    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...
  2. sergey_le

    Chemical kinetics lab question

    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...
  3. E

    Can we effectively use solar power for Sulphur-Ammonia Thermocycle?

    We are required to design a facility to produce hydrogen via Sulfur-ammonia 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...
  4. J

    Which mechanism and which step would best fit the data?

    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...
  5. D

    Chemical Kinetics: velocity and equilibrium

    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...
  6. B

    Kinetics question (Chemical engineering)

    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 0,030M-solution of X was calculated with the help of a Spectrometer. The Spectrometer was...
  7. sidt36

    Kinetics problem from olympiad

    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 *10-2) + 1/x = k(half life time) Is this the right approach Please help me...
  8. K

    Chemical Kinetics: Understanding the Reaction of A & B

    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...
  9. MexChemE

    Mass balance with reaction -- Chemical kinetics POV

    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...
  10. mooncrater

    A statement of chemical kinetics

    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...
  11. H

    AP Chemistry Chemical Kinetics Problem

    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...
  12. F

    Can a Graph of Concentration vs. Time Reveal a Balanced Chemical Equation?

    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...
  13. F

    Solve 2nd Order Reaction Kinetics: Mn(CO)sub5 → Mnsub2 (CO)sub10

    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 =...
  14. M

    Chemical kinetics, reaction order, resistance

    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/81386cf6-e132-4578-8fb5-1024a2a3f3d5_zpscc804723.jpg.html?sort=3&o=0 3. So my attempt included graphing -R/(R∞-R) vs. time. which produced...
  15. B

    Chemical Kinetics: determining order of reaction

    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...
  16. H

    Chemical Kinetics Homework: Ineq., Mass & English

    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
  17. O

    Chemical Kinetics - Concentration/time

    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)...
  18. U

    Chemical Kinetics Radioactivity

    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...
  19. N

    Chemical Kinetics QuestionDetermination of order of reaction

    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...
  20. S

    Solutions and colligative properties and chemical kinetics combined ques.

    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...
  21. N

    Chemical Kinetics Qn: Why is D Not a Possible Answer?

    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...
  22. A

    Chemical Kinetics - Activation Energy and gr

    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...
  23. M

    The collision theory of chemical kinetics

    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...
  24. L

    Chemical kinetics diagramm -> chemical equation

    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...
  25. R

    Find Remaining NO Concentration: 2NO + 2H2 → N2 + 2H2O, 0.006M NO, 0.002M H2

    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 one-half 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...
  26. P

    Chemical Kinetics, finding rate of reaction

    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...
  27. C

    Chemical kinetics - reaction rate

    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...
  28. S

    Why is the denominator of the ratio possible if the forward rate is 2nd order?

    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...
  29. Z

    Chemical Kinetics Advanced Problem

    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...
  30. A

    Chemical Kinetics: 2A to C Reaction Rate Law

    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...
  31. B

    Chemical Kinetics: do not understand anything

    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...
  32. W

    Chemical Kinetics: Rate Laws, Orders

    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...
  33. A

    Understanding Chemical Kinetics: Troubleshooting Common Questions in the Lab

    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...
  34. J

    Chemical Kinetics (Reaction Mechanisms)

    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!
  35. T

    Chemical Kinetics: Reaction Mechanism (My working attempt shown)

    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 highly-energized form of A. Step 1 (reversible): A + M <---> A* + M rate constants k1 and k-1 Step...
  36. T

    Chemical Kinetics: Reaction Mechanism

    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 highly-energized form of A. Step 1 (reversible): A + M <---> A* + M rate constants k1 and k-1 Step...
  37. H

    Chem Kinetics: Suggestions for Further Reading & Calculus-Based Texts

    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...
  38. A

    Smaller Packing Fraction, Higher Nuclear Stability - Chemical Kinetics

    why smaller the packing fraction higher the stability of nucleus ?
  39. M

    Solving Chemical Kinetics Homework for A, B, C & D

    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)...
  40. V

    Arrhenius Equation - Chemical Kinetics

    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...
  41. K

    Chemical Kinetics - Rate Laws and Mechanisms

    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...
  42. F

    Identifying Intermediates in chemical kinetics

    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...
  43. F

    How do I solve these Chemical Kinetics homework problems?

    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...
  44. S

    How Does a 10°C Temperature Increase Double the Rate of a Slow Reaction?

    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...
  45. maverick280857

    Chemical Kinetics Query

    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...
  46. Link

    Quick Chemical kinetics question

    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...
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