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. B

    Exact Solutions for Kinetics of 2A + B → C + D Reaction with Rate Constant k

    If I have a reaction where R(Gain of C)=k(Gain of C)*A2*B, where k is the rate constant and the reaction is 2A + B → C + D, how can I get two exact expressions, for the concentrations of A and B respectively, in terms of time, the initial values of A and B, and k? This will be an ODE I imagine...
  2. B

    Kinetics ODE Solutions: Understanding Rates and Concentrations in Chemistry

    I've got this problem, with relation to rates. [A] is the concentration of one substance, is the concentration of another, etc. [R] is a general reactant, [P] is a general product, [S] is a general substance (which thus relates to both reactants and products). But you won't actually need...
  3. D

    Solving Collision and Kinetics Problems in 2D

    Hello Everyone, I am having a heck of a time with collisions in 2D and with rotational kinetics and rotational dynamics. I have posted 5 questions below that I seem to be having the most troubles with. I know it my be a lot to ask but if anyone here can help me to understand how they got to...
  4. L

    Kinetics friction question: derive acceleration of aircraft

    1. Hello there, I am a first year undergraduate mechanical engineering student, looking for help on a question. "Figure Q2 shoes a schematic diagram for an aircraft catapult system. The aircraft is represented by the mass A (Ma), and μ is the coefficient of friction between the aircraft and...
  5. K

    Physical Chemistry: Kinetics and fluorescence

    Homework Statement Consider fluorescence (light emission from an electronically excited state of a molecule) in the presence of a quenching molecule M. Quenching refers to the removal of energy from an excited electronic state by collision, and so without light emission. A mechanism for such...
  6. L

    4 Point masses form a body - Inertia & Rotational Kinetics

    Homework Statement Four point masses form a rigid body (they are connected by massless rigid rods) given the positions M1= 3kg (2m, 4m, 0m) M2= 2kg (1m, -4m, 0m) M3= 1kg (10m, 2m, 0m) M4= 5kg (-5m, 2m, 0m) Find: A) Moment of inertia of this system when it rotates about x axis B) Moment of...
  7. 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)...
  8. M

    Equilibrium constant vs rate constant - where kinetics meets thermodynamics?

    Equilibrium constant vs rate constant - where kinetics meets thermodynamics?? The Equilibrium Law for aA + bB ⇌ cC + dD gives Kc = [C]c [D]d / [A]a x [B]b at a given temperature. Kc* is also equal to the ratio of forward to reverse rate constants kfwd/krev. The rate expression for the forward...
  9. 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...
  10. H

    Kinetics of Pchem Ques: Adsorption, Desorption, Rate Consts

    1. question http://farm9.staticflickr.com/8282/7804721900_bd0b895954_b.jpg On a catalyst surface, the formation reaction of CO2 by the oxidation of CO with O2 proceeds in the following mechanism. (1) O2(g) + 2V <---> 2O(ads) (equilibrium constant KO2) (2) CO(g) + V <--> CO(ads)...
  11. F

    Kinetics of methyl benzoate synthesis

    Hello, is there anyone knows the kinetics data of methyl benzoate synthesis by fischer esterification?? (activation energy & E estimation methode, or any experiment that involve temperature variance),, I had trouble in calculate reaction rate constant by the function of temperature... I only...
  12. P

    How Do You Calculate the Final Angular Velocity of a Spinning Top?

    Homework Statement A top is a toy that is made to spin on its pointed end by pulling on a string wrapped around the body of the top. The string has a length of 64 cm and is wrapped around the top at a place where its radius is 2.0 cm. The thickness of the string is negligible. The top is...
  13. 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...
  14. 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...
  15. 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...
  16. 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...
  17. 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...
  18. K

    What mistakes may be causing discrepancies in the solution for the force P?

    Homework Statement The linkage ABD is formed by connecting two 8.05-lb bars and a collar of negligible weight. The motion of the linkage is controlled by the force applied to the collar. Knowing that a tthe instant shown the angular velocity and angular acceleration of bar B are zero and 10...
  19. F

    Troubleshooting Tension: A Closer Look at Rotational Motion Calculations

    Homework Statement The tension answer I got is different from the answer. Can someone help me take a look at my working? Really appreciate your time in doing this. Thanks alot.
  20. B

    Folding Kinetics: Equation & Chevron Plot

    Homework Statement Folding can be described as transition between the native and unfolded state. In increasing concentrations of denaturant, a fold disintegrates with a rate lnKU = ln KU H20 - m ku [denat] when the concentration of denaturant is above that needed to unfold 50 % of...
  21. B

    Folding Kinetics: Equations, Chevron Plots & Mutation Effects

    1. Folding can be described as transition between the native and unfolded state. In increasing concentrations of denaturant, a fold disintegrates with a rate lnKU = ln KU H20 - m ku [denat] when the concentration of denaturant is above that needed to unfold 50 % of protein. Conversely...
  22. Femme_physics

    Basic Kinetics Question: Calculate Velocity on a Circular Path - Homework Help

    Homework Statement http://img39.imageshack.us/img39/3778/funkyrider.jpg So I got this funky rider that starts its movement from the top of the hill A at initial speed (Vo). From that point, the bicycles role on freely (without using pedals) at the circular path. Calculate the velocity...
  23. P

    Simple kinetics problem / Dynamics /

    Simple kinetics problem / Dynamics / Simultaneous equations I've been trying to solve this problem for hours, not finding the solution. Therefore this question to PhysicsForums homeworks section. Question is just part of the problem, but in order to fully understand issue I must have these...
  24. Femme_physics

    Elementary kinetics problem - Using calculus is different result from algebra

    Homework Statement http://img42.imageshack.us/img42/8172/carxp.jpg Homework Equations In my solution The Attempt at a Solution My attempt: http://img208.imageshack.us/img208/6526/xxxxoh.jpg The actual solution http://img403.imageshack.us/img403/5579/carsol.jpg...
  25. M

    How to Solve Angular Kinetics Problem with Inclined Plane and Hoop Release

    Homework Statement A hoop is released from rest at the top of a plane inclined at 16 above horizontal. How long does it take the hoop to roll 16.4 m down the plane? Homework Equations The Attempt at a Solution I know I have to find the final velocity, I know the Inertia is =...
  26. N

    Ap physics questions on basic kinetics and Newtons second law

    1)A rock is dropped off a cliff and falls the first half of the distance into the ground in t1 seconds. If it falls the second half of the distance in t2 seconds, what is the value of t2/t1? Relevant equations: I think the kinematics equations of d=vt+(1/2)at^2 I have no idea how to solve...
  27. I

    Plane kinetics of rigid bodies

    Homework Statement The uniform 3.6m pole is hinged to the truck bed and is released from the vertical position as the truck starts from rest with an acceleration of 0.9m/s^2. If the acceleration remains constant during the motion of the pole as it reaches the horizontal position what is the...
  28. S

    Solve Kinetics Homework Question | t=17.5, 11.3s

    Homework Statement I trying to do this hibbeler question which I have modified a bit However I'm not getting the correct answers which is supposed to be t=17.5 and t=11.3 s I will take a picture of my attempt when I get a hold of a camera in the meantime if anyone knows how to do it I...
  29. A

    What equation to use for simple kinetics quesitons?

    For the questions below, which kinematic equations would I use? I have already tried these on my own but can not find a way to match the answers with the answer sheet, the answers on the answer key are RIGHT, as they are approved by my teacher. Okey so the questions are 1) A baseball is...
  30. 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...
  31. D

    MHB Identifying Closed Orbits in Enzyme Kinetics Equations

    \begin{align} \dot{x} =& -x + ay + x^2y\notag\\ \dot{y} =& b - ay - x^2y\notag \end{align} The only steady states are $(-b,0)$ and $\left(0,\frac{b}{2a}\right)$, correct? I feel like there should be more but I don't think there any.
  32. 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...
  33. R

    Descriptive kinetics notes needed

    We are currently going over Kinetics in my AP Chemistry class but I am struggling with kinetics, our book is not very clear and tackles on several ideas at once making it hard to understand. My teacher is also not very helpful, sadly. I have been searching for some notes on Kinetics but have not...
  34. N

    How Does Michaelis-Menten Kinetics Describe Enzyme-Substrate Interaction Rates?

    Homework Statement For the reaction between enzyme and substrate: E + S <-> ES -> E + P E = enzyme, S = substrate, ES = enzyme-substrate complex, and P = product. Where E + S -> ES rate constant = k_{1} For ES -> E + S = k_{-1} For ES -> E + P = k_{2} Homework Equations My...
  35. R

    How Do You Calculate the X and Y Components of Forces in a Pully System?

    Hi guys, Got a general question here about sum of forces that keeps coming up for me, and so I want to try and nail it this time. If you have a pully system, and there is a weight attached to a rope at one end of say 10 kg and the other end is is attached to a force of 1000 N that is...
  36. R

    Kinetics of Rigid Bodies: Torque and Acceleration Calculation

    Homework Statement The rotor of an electric motor of mass 200 kg has a radius of gyration of 150 mm. Calculate the torque required to accelerate it from rest to 1,500 rev/min in 6 seconds. Friction resistance may be neglected. Homework Equations ƩMO = Iα I = 1/2 (mr2 I am really really...
  37. 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...
  38. 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...
  39. S

    Enzyme Kinetics: Measuring Inhibitory Effects and Determining Km and Vmax Values

    Somebody please help me. Practical: A calibration graph should be prepared by taking 0.0 (zero, blank), 1.0, 2.0 and 3.0 ml aliquots of an aqueous solution containing both 1.67 mM D-glucose and 1.67 mM D-fructose. Add distilled water to maket it 3 ml. Add 1 ml DNS reagent. Incubate 5 min...
  40. M

    Fermentation kinetics info resources?

    Howdy all, Recently I have dabbled in homebrewing mead and it turned out... drinkable at best. I am making another batch soon and want to improve my methods. I am a nuclear engineering student, so naturally I feel that something as personal, liberating, and chemically miraculous as...
  41. S

    Enzyme kinetics plotting a slope replot

    hi, My instructor has given us an assignment where we have to diagnose the type of enzyme inhibition it is. I diagnosed it as a competitive inhibitor and am trying to do a slope replot to find my value for KI. For the slope replot, you just find the slope of the each line? is it the same...
  42. M

    Kinetics and Projectile Motion

    I've got nothing mates. Any help would be great.
  43. S

    Kinetics Assignment - Reaction Orders

    Homework Statement The concentration of the reactant A has been studied as a function of time. By a suitable plot of the data below, show that the reaction is first order, and determine the rate constant, k, and the half-life, t1/2. Use the integrated rate equation to determine [A] when t =...
  44. B

    N Angular Kinetics: Calculating Force Needed to Maintain 45° Position

    A 35N hand and forearm are held at a 45 degree angle to the vertically oriented humerus. The centre of gravity of the forearm and hand is located at a distance of 15cm from the joint centre at the elbow, and the elbow flexor muscle attach at an average distance of 3cm from the joint centre. How...
  45. T

    Exercise on Kinetics using derivatives.

    Homework Statement The acceleration of a body is defined as a=-K*u^2 , K is const. When t=o sec V=Vo. Find : a) V(t) b) X(t) c) V(x) . Homework Equations The Attempt at a Solution
  46. M

    General Chem Kinetics question.

    Question 1: Step 1: 2NO2 (g) + 2SO2 (g) = 2NO (g) + 2SO3 (g) Step 2: 2NO (g) + O2 (g) = 2NO2 (g) The reaction is found to be first order with respect to NO2 and SO2, what is the slow step for this reaction? 1. First step 2.Second step 3.Not possible to determine Question 2 and 3...
  47. S

    Solving Rigid Body Kinetics: Pulley Tension & Moment of Inertia

    hey guys, please see the attachment for the question. i drew FBDs and everything. i want to know a few things tho. how do i calculate the tension in the pulley? if they'd given me acceleration i could have used T-mg =ma. but they havent. also once the Tension is found, do i just find the...
  48. A

    Kinetics with Veloctiy/Acceleration Problem

    Hello, I need help on this following problem on velocity/acceleration 1. Homework Statement The velocity function (in meters per second) is given for a particle moving along a line. v(t)=3t-11, 0 (greater than or equal to) t (greater than or equal to) 5 Find the distance (in meters)...
  49. F

    Kinetics with Total Gas Pressures

    Homework Statement I am considering the reaction 2C4H6 --> C8H12 at 320 degrees C. Both the product and the reactant are gases. I have the data: Time (minutes): 0.00 3.25 12.18 24.55 42.50 68.05 Total P (torr): 632.0 618.5 584.2 546.8 509.3 474.6...
  50. R

    Luminescence decay kinetics with bimolecular terms

    Hi I wonder if anyone could help me with this. I'm studying a crystal whose luminescence is excitonic in nature. Since the excitation density is high (with femtosecond laser pulses) exciton-exciton interactions have to be taken into account. The following kinetic equations are used to...
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