What is Kinetics: Definition and 254 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. 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...
  2. RoboNerd

    Effects of Crushing a Solid on Equilibrium Position

    Hi everyone. So I have been learning about equilibrium recently in class... and suppose I have the following reaction: A(s) + B(aq) <-----> C(aq) + D(g) [Note: in parentheses, I indicate the state of my substances] So I was told recently that pulverizing my solid "A" would not change the...
  3. 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...
  4. A

    Activation energy of parallel reaction

    Well,I know that the activation energy of a parallel reaction can be determined by the arrhenius equation as (e1k1+e2k2)/(k1+k2) where e1,k1 and e2,k2 are the activation energies and rate constants for the two reacations.now consider the reaction A》B,and A》C since at every instant the reacted...
  5. D

    Banked Curve - Minimum Turn Radius

    Homework Statement A car traveling 10 m/s is moving along a track banked at 5 degrees. The tire-road friction coefficient is .3 What is the minimum radius it can travel without slipping? v0= 10 m/s Bank Angle Θ = 5° μ=0.3 Note I am working through prep material for the exam. The solution...
  6. Dopplerganger

    Recognize this irreversible equation for kinetic modeling?

    Hi all, I'm trying to come up with velocity equations for a multi-enzymatic system and came across this velocity equation. Does anyone recognize this equation? There was no citation or derivation and the variables were not explained. This is my guess: P, Q, A, B are concentrations of some...
  7. D

    Finding the angle of projection and its speed in 2D Kinetics

    Homework Statement : The trajectory of a projectile in a vertical plane is y = √3 x - (1/5)x2, where x and y are respectively horizontal and vertical distances of the projectile from the point of projection. Find the angle of projection and speed of projection.[/B]Homework Equations ...
  8. S

    Kinetics of a rigid body (conservation of energy)

    Homework Statement [/B]Homework Equations [/B] (1) (pink) Is it vertical displacement ? * 4 - 2 (unstretched length of the spring) ? (2) (blue) What does it mean ? * I was thinking that maybe they used The Pythagorean theorem (62+42)=7,2 ≅ 7) but I'm not sure. Besides I don't understand...
  9. A

    Enzyme kinetics Km Vmax Alcoholdehydrogenase

    So in the lab I have measured my first enzyme reaction rates to determine the Km and Vmax of ADH. We are using yeast ADH. We are measuring it using DCIP coupled to NADH production using PMS. So NADH does not accumulate and we measure tha lowering in DCIP concentration using spectroscopy...
  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. mooncrater

    Solve Kinetics Question: Zero Order Reaction at High Pressure

    Homework Statement The question says: The decomposition of a gas on a surface follows the rate law : Rate is proportional to ##\frac {kP}{1+kP}##, where ##P## is the pressure and ##k## is a constant. Find the order of the reaction at high pressure. Homework EquationsThe Attempt at a Solution...
  12. A

    Deriving a Rate Equation for a Reversible Elementary Mechanism

    Homework Statement Overall reaction: A + F = I + J (just take = as the equilibrium sign) It is first order in both A and B. The following mechanism has been proposed: 1. A + B = C + D 2. C + D = E + B (B is the catalyst) 3. E + F = G + H 4. G + H = I + J These are all...
  13. M

    Kinetics Problems -- Blocks on inclined plane

    Homework Statement Problem 1: A block of mass m = 15 kg from rest on an incline of 20 °. It is assumed that static and dynamic friction coefficients are respectively μs =0.4 and μk = 0.2. a force P is then applied (P = 30 N) on the block as shown in Figure 1 . a) Will the block slide? (...
  14. A

    Kinetics question: calculating rate constants

    Homework Statement I need help for this kinetics question: Chlorination of butene at 0 degrees c, liquid phase, dichloromethane as solvent. initial concentration of butene is 0.1M conversion of 47.71% achieved after 3.1 hours. an additional 0.5M of hot butene was added at this point, which...
  15. A

    Difference between statics, dynamics, kinematics and kinetics

    Dear All, I am often get confused when four terms STATICS,DYNAMICS,KINEMATICS and KINETICS are used in physics Mechanics.can someone please differentiate between these four terms.i will be thankful.
  16. _N3WTON_

    Kinetics: Two Blocks and a Spring

    Homework Statement Suppose a block of Uranium and a block of Radium, both with edge length \lambda , are pushed to the head of an un-stretched spring (spring constant k , un-stretched length \delta _0 ). The combination, pushed \delta farther, compresses the spring. Upon release, the...
  17. C

    Reaction kinetics for reppe synthesis of propionic acid

    I need help finding the kinetics(rate laws) of this process. I've been searching for close to a week and can't seem to find them. It the carbonylation of ethylene to produce propionic acid(pretty much any variant of the process will do). I have access to my schools publication library so the...
  18. L

    Enzyme Kinetics- is my summary correct?

    I have been looking at this enzyme kinetics stuff forever and was trying to come up with a summary for things... #=_= Is this even right...? :/ |---------------|This segment I'm calling "Part 2" k1 k2 E + S ES E + P k-1 |---------------|This...
  19. L

    Kinetics Problem: Non-constant force (calculus)

    Homework Statement A rock with mass m slides with initial velocity v0 on a horizontal surface. A retarding force F that the surface exerts on the rock is proportional to the square root of the instantaneous velocity of the rock (F = -kv1/2) . a) Find expression for the velocity of the rock as a...
  20. 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...
  21. S

    Graphing the Results from Kinetics Experiments with Enzyme Inhibitors

    Homework Statement The following kinetic data were obtained for an enzyme in the absence of any inhibitor (1), and in the presence of two different inhibitors (2) and (3) at 5mM concentration. Assume [ET] is the same in each experiment[/B] (1)...
  22. P

    Exploring Equilibrium Constants & Kinetics: A Closer Look

    Consider the following generic equilibrium: aM + bN ⇌ cO + dP An equilibrium constant, K, can be defined as: $$K = \frac{[O]^c [P]^d}{[M]^a [N]^b}$$ But couldn't we also define another equilibrium constant similarly with coefficients that are in the same ratio as our original equation? For...
  23. K

    Kinetics Problem: Finding time distance and initial velocity

    Homework Statement You are riding in a hot air balloon at an altitude of 167 meters traveling at a horizontal speed of 24 m/s. If you fall out of the basket, how long will it take you to hit the ground? How far will you travel horizontally in this time. What is your total speed when you hit the...
  24. U

    Kinetics Question: Solving for Velocity and Displacement

    Homework Statement Homework Equations The Attempt at a Solution v = ds/dt ∫v dt = ∫ds (put all inital values for V) ∫70-70e^t dt = ds 70t - 70t*e^t = s There is something wrong with my methodology. can you guide me here?
  25. 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...
  26. 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 =...
  27. C

    Plotting x vs 2*x is it possible? (Reaction kinetics)

    Hi, I red in reaction kinetics that if you plot the concentration of A againts "some constant times the concentration of A", the constant will be the slope of a straight line (check out the photo i attached). This threw me a bit off, so let me just make sure i understand this: So i assume...
  28. B

    Equilibrium Stat Mech Vs. Kinetics

    Ensembles Figured it out thanks, next post:
  29. C

    3 Questions regarding reaction kinetics- me out.

    Hi I need some help understanding reaction kinetics, and I’m trying to get an overview, so I’d really appreciate some help. I have 3 individual/quite unrelated questions, if you have time to answer one that would be very much appreciated. 1. In what situations dos the Definition of the...
  30. M

    Calling kinetics experts: rate law from conductivity isnt possible?

    Calling kinetics experts: rate law from conductivity isn't possible!? Consider the usual primary halogenoalkane aqueous alkaline hydrolysis reaction RX + OH- --> ROH + X- We know the rate law is first order in RX and OH-. We could separately represent the drop in OH- conductivity as an...
  31. C

    Solving Kinetics & Arrhenius Equation: Find A & Ea

    Homework Statement The activation energy and Arrhenius paramter can be found from its temperature dependence the Arrhenius equation k=Aexp(-Ea/RT) --> lnk=lnA - Ea/RT Given data is 5 temperatures with their corresponding k values Q1) From this data calculate A and Ea q2) Here A has...
  32. B

    Competitive Kinetics: Solve Rate Equation and Mass Balance

    Please see the attached problem. Rate is being defined as d[P]/dt, and d[P]/dt = k3[ES]. So the main challenge is expressing [ES]. I applied the steady-state approximation to find [ES] = [E][S]k1+k-2[ES2] / (k3+k-1+k2[S]). The other equation I've used is [E]0=[E]+[ES]+[ES2], the E mass...
  33. 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...
  34. D

    Kinetics Question: Rate of Reaction at 0.503 M

    Homework Statement Consider the following reaction at 282 K. 2 A + 2 B → C + D where rate = rate=k[A][B]2. An experiment was performed for a certain number of seconds where [A]0 = 0.000303 M and [B]0 = 1.63 M. A plot of ln[A] vs time had a slope of -7.27. What will the rate of this...
  35. Z

    How Does Langmuir Kinetics Apply to Adsorption Processes?

    Homework Statement Adsorption of many solutes is governed by Langmuir kinetics given below. Equation 1 dq/dt=ka (qm−q )c−kdq If a batch of adsorbent pellets of mass M is added to a solution of adsorbate, at an initial concentration ofc0 and volume V, the mass balance yields: Equation...
  36. 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...
  37. B

    Kinetics Assumptions: Approximations & Equilibria

    I would like to understand under what circumstances rate laws can leave out rate terms from certain reactions, in general, as a process of approximation. I am familiar with the basic method regarding the steady-state approximation already. Any books, websites or articles which are good or...
  38. S

    Difficult problem on Angular Kinetics

    Hi, I was working on a problem and I am having trouble in being able to solve this problem. The difficulty is that the question only presents not enough data to find the answers that it asks for. Homework Statement Here is the problem in it's entirety: A wheel whose moment of inertia is...
  39. 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
  40. C

    Physical Chemistry- Rates and Kinetics

    Homework Statement The Reaction; 2NO(g) + Cl2 (g) → 2NOCl (g) Is second order in NO and first order in Cl2. Five moles of nitric oxide and two moles of Cl2 were brought together in a volume of 2dm3 and initial rate was 2.4x10-3 moldm-3sec-1. What will be the rate when one half of the...
  41. N

    Dynamics: Planar Kinetics of a Rigid Body(Work and Energy)

    Homework Statement The operation of this garage door is assisted using two springs AB and side members BCD, which are pinned at C. Assuming the springs are unstretched when the door is in the horizontal (open) position and ABCD is vertical, determine each spring stiffness k so that when the...
  42. L

    Rigid Body Kinetics: Find Reaction Force at A

    Homework Statement As the picture says, we are trying to find the reaction force on the bearing at A: We are given: M(block) = 26.1kg M(bar) = 8.7kg L(bar) = 1.8m V(block) = 6.2m/s Homework Equations What I have attempted the solution with are: ƩF = ma ƩM = Iα I0 = (m*L^2)/12...
  43. G

    Biochemical Engineering - Heterogeneous Reaction, MM Kinetics

    I'm doing an essay on imobilized enzymes. I need to evaluate some data i collected, to do that i need a graph that can relate effectiveness and Thiele's Modulus. My problem is that the only graph that i could find was this one: http://imgur.com/aykaMvU As you can see there's no graduation on...
  44. G

    Rigid Body Kinetics: Angular Acceleration of Rod w/ Friction Torque

    Homework Statement A long slender rod has a mass of 0.66 kg and a length of 648.0 mm. The friction torque at the hinge is 0.41 Nm. What is the angular acceleration of the rod when it is 38 degrees below the horizontal? Homework Equations The Attempt at a Solution Torque =...
  45. M

    Zero order kinetics - theory query

    If equimolar amounts of iodine and propanone are reacted in acidic conditions, the [propanone] vs time graph would be expected to show an exponential decay as expected from first order kinetics. The [iodine] vs time graph vs time must therefore also be an exponential decay in order to obey the...
  46. L

    Nonlinear coupled differential equation system - kinetics

    Dear All, Recently, I have measured a series of nonlinear vibrational spectra from which I would like to extract some useful information about kinetics of the exchange process occurring in the studied system. I need to fit my experimental data to kinetic model that is a solution of coupled...
  47. W

    How Does the Ideal Gas Theory Account for Volume and Mass?

    This might be a stupid question, but I am confused about the ideal gas theory. I know that we assume high temperatures and low pressures, and that the volume is negligible when we compare it to a container, but my textbook is very confusing about this point. It says assume zero/negligible...
  48. O

    Molecular flux-thermodynamic kinetics

    1. Homework Statement A volume is divided into two equal parts by a partition. The left volume has N atoms. The atoms have a mass m. A hole of area A is made in the partition at time t=0 A)Develop an expression for the number of white atoms on each side of the partition at time t...
  49. O

    Molecular flux-thermodynamic kinetics

    Molecular flux--thermodynamic kinetics Homework Statement A volume is divided into two equal parts by a partition. The left volume has N atoms. The atoms have a mass m. A hole of area A is made in the partition at time t=0 A)Develop an expression for the number of white atoms on each...
  50. B

    Kinetics, Complex Reactions, Approximations

    I wasn't sure where to ask this question as I don't know where else to make requests like this, so I thought I would go here. Please feel free to move it to a more appropriate forum if there is one. My syllabus states the following point: ------ Analysis of complex reactions using...
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